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Biomedical subjects

R Hakim

Publications and source records attributed to R Hakim.

At least 19 recordsLinked to original sources
PubMed2004

Circadian variations of rectal cell proliferation in patients affected by advanced colorectal cancer.

The circadian rhythm of the rectal cell proliferation was studied in five patients affected by advanced colon cancer. Biopsies were taken from apparently normal mucosa at 10 cm from the anal verge, every 6 h in a 24-h period. Fragments were incubated for 1 h in a culture medium containing bromodeoxyuridine (BrdUrd). As compared with the mean 24 h values, the percentage of BrdUrd-labelled cells in the crypts (Labelling Index, LI) was lower in the specimens collected at 10.00 PM (P = 0.02) The LI in such biopsies was also lower than the LI observed at the baseline time, 10.00 AM (P = 0.001) The results suggest that the rectal cell proliferation in patients with advanced colon cancer fluctuates during the day. The study of the rhythmicity of the intestinal cells may be useful to modulate the infusion of antiproliferative agents to prevent damage of the normal colorectal mucosa.

Aged↗
PubMed2002

Cancer surveillance in ulcerative colitis: critical analysis of long-term prospective programme.

BACKGROUND: Patients with longstanding ulcerative colitis are at increased risk of colorectal cancer. In the literature, no agreement has yet been reached regarding prevention strategies. Our report sums up a prospective study started in 1980. METHODS: A total of 65 patients affected by ulcerative colitis for more than seven years were admitted to a regular colonoscopic and biopsy follow-up programme. RESULTS: Some 20 years after the beginning of the study, 23 (35.3%) patients have been operated upon, 2 patients have died but not from cancer 29 (44.66%) patients have abandoned the programme. Only 11 (16.9%) patients have remained under colonoscopic surveillance. CONCLUSION: These results cast some doubts on the significance of such a programme and on its long-term feasibility.

Aged↗
PubMed2001

Normal-pressure hydrocephalus.

This article presents a brief history of normal-pressure hydrocephalus, its clinical presentation, and different theories on its pathophysiology. The different diagnostic tests, differential diagnosis, and its treatment are presented.

Brain↗
PubMed2000

Effect of radiographic contrast agents on leukocyte metabolic response.

BACKGROUND: The use of radiographic contrast media in the setting of possible bowel ischemia and potential perforation is known to carry a risk of morbidity and mortality. However, studies of the effect of available contrast media on host immunological defense mechanisms are lacking. We have examined the effect of barium and of two water-soluble contrast agents of differing iodine concentration and osmolality, Conray 30 and Cysto Conray II, on leukocyte phagocytosis. MATERIALS AND METHODS: Blood samples were incubated with the contrast media alone (termed the "resting state"), and in combination with a standard phagocytic challenge (Zymosan polysaccharide extract) and with Staphylococcus epidermidis, Streptococcus faecalis and Escherichia coli, to determine the effect of contrast media upon leukocyte phagocytic response. Incubation with saline was used as control. In the case of barium, the "resting state" and standard challenge experiments were repeated at nine dilutions, ranging from 1:1 to 1:1000. The leukocyte phagocytic response was measured in two ways: CO2 generation (an index of metabolic activity) and chemiluminescence (an index of generation of reactive oxygen species and bacterial killing). RESULTS: Barium, at clinical dilutions, causes a significant increase of baseline "resting state" phagocytic activity, which in turn leads to significant blunting of subsequent response to phagocytic challenge and adversely affects the response to all bacteria tested. There is no baseline activation of leukocytes by the water-soluble media, although there was some inhibition (rather than activation) of leukocyte metabolic activity. The effect of the water-soluble media on bacteria was more complex (although inhibition is minor compared to barium). CONCLUSIONS: Our data demonstrate that barium is a significant activator of phagocytic cells, which results in deactivation of phagocytic response when challenged; these data serve to explain the enhanced adverse effect of barium in cases of fecal peritonitis.

Barium Sulfate↗
PubMed2000

Physician understanding of patient resuscitation preferences: insights and clinical implications.

OBJECTIVE: To describe physician understanding of patient preferences concerning cardiopulmonary resuscitation (CPR) and to assess the relationship of physician understanding of patient preferences with do not resuscitate (DNR) orders and in-hospital CPR. DESIGN: We evaluated physician understanding of patient CPR preference and the association of patient characteristics and physician-patient communication with physician understanding of patient CPR preferences. Among patients preferring to forego CPR, we compared attempted resuscitations and time to receive a DNR order between patients whose preference was understood or misunderstood by their physician. PATIENTS/SETTING: Seriously ill hospitalized adult patients were enrolled in the Study to Understand Prognoses and Preferences for the Outcomes of Treatments. GENERAL RESULTS: Physicians understood 86% of patient preferences for CPR, but only 46% of patient preferences to forego CPR. Younger patient age, higher physician-estimated quality of life, and higher physician prediction of 6-month survival were independently associated with both physician understanding when a patient preferred to receive CPR and physician misunderstanding when a patient preferred to forego CPR. Physicians who spoke with patients about resuscitation and had longer physician-patient relationships understood patients' preferences to forego CPR more often. Patients whose physicians understood their preference to forego CPR more often received DNR orders, received them earlier, and were significantly less likely to undergo resuscitation. CONCLUSIONS: Physicians often misunderstand seriously ill, hospitalized patients' resuscitation preferences, especially preferences to forego CPR. Factors associated with misunderstanding suggest that physicians infer patients' preferences without asking the patient. Patients who prefer to forego CPR but whose wishes are not understood by their physician may receive unwanted treatment.

Activities of Daily Living↗
PubMed1999

Intradialytic serial vascular access flow measurements.

Hemodialysis vascular access failure represents a major source of morbidity and mortality in chronic hemodialysis (CHD) patients. Serial vascular access blood flow (VABF) measurements are being used as a screening method at an increasing rate. There are limited data on the changes in VABF throughout the hemodialysis session, which may potentially affect the validity of VABF measurement. This study is performed to evaluate the trend in VABF during a given hemodialysis session by serial VABF measurements, along with potential factors that may affect VABF. Thirty-two CHD patients had serial VABF measurements performed during a hemodialysis session. Each patient had three serial VABF measurements during a hemodiaysis treatment (within 30, 90, and 150 minutes from the start of hemodialysis). Mean arterial blood pressure (MAP), ultrafiltration rate, and patient symptoms were recorded simultaneously. The mean VABF was 1,344 +/- 486 mL/min within 30 minutes of hemodialysis and decreased to 1,308 +/- 532 and 1,250 +/- 552 mL/min after 90 and 150 minutes, respectively. This trend was statistically significant (P = 0.03). There was a strong correlation between VABF measurements and MAP, which was more pronounced after 90 minutes of initiation of hemodialysis (r = 0.68; P < 0.001). Using multivariate analysis, it can be predicted that after 90 minutes of hemodialysis, each 10% decrease in MAP would result in an expected decrease of 8% in VABF. There was no effect of type of vascular access, baseline VABF, or amount of ultrafiltration on VABF changes. In conclusion, VABF measurements can be performed up to 2 to 2(1/2) hours from the start of hemodialysis in the majority of patients. The major determinant of VABF changes is MAP. In a subset of patients with a decrease MAP greater than 15%, it is advisable to perform VABF measurement either at the first 90 minutes of hemodialysis or postpone it to another treatment session, when MAP is more stable.

Adult↗
PubMed1999

Increased susceptibility to erythrocyte C5b-9 deposition and complement-mediated lysis in chronic renal failure.

BACKGROUND: Decreased red blood cell survival contributes to the anemia of chronic renal failure patients. Because patients on chronic dialysis therapy are frequently exposed to excessive complement activation, we investigated the susceptibility of this patient population to erythrocyte C5b-9 deposition, complement-mediated lysis, and ghost formation. METHODS: We developed a flow cytometric assay using antibodies to both glycophorin and the C5b-9 complex to detect C5b-9 deposition on intact erythrocytes and erythrocyte ghosts. Serum C5b-9 levels and C5b-9 deposition on erythrocyte ghosts were measured by enzyme-linked immunosorbent assay. RESULTS: A significant increase in C5b-9 deposition on intact erythrocytes was demonstrated in patients with advanced chronic renal failure (2.2 +/- 0.5%) and in patients on chronic maintenance hemodialysis (2.3 +/- 0.4%) compared with normal volunteers (0.9 +/- 0.1%, P = 0.005 vs. chronic renal failure, P < 0.001 vs. chronic hemodialysis patients). There was also a significantly higher percentage of C5b-9-positive erythrocyte ghosts in patients with advanced chronic renal failure (20.6 +/- 5%) and in chronic hemodialysis patients (15.5 +/- 3.1%) compared with normal controls (2.6 +/- 0.9%, P < or = 0.001 vs. advanced chronic renal failure and chronic hemodialysis patients). Treatment of erythrocyte preparations with cobra venom factor, which activates the complement cascade, resulted in dramatic increases in the percentages of C5b-9-positive erythrocyte ghosts in patients with chronic renal failure (49.9 +/- 6.9%) and in chronic hemodialysis patients (45.0 +/- 4.2%) compared with normal volunteers (22.3 +/- 2.7%, P < 0.001 vs. chronic renal failure and chronic hemodialysis patients). Erythrocyte membrane expression of the complement regulatory proteins CD59 and CD55 did not significantly differ between normal controls and hemodialysis patients. Plasma C5b-9 levels after cobra venom factor stimulation were higher in chronic renal failure patients (538 micrograms/ml) compared with normal controls (345 micrograms/ml, P < 0.001). CONCLUSIONS: Patients with chronic renal failure and on hemodialysis therapy are susceptible to erythrocyte C5b-9 deposition with subsequent lysis and ghost formation. Susceptibility to complement-mediated erythrocyte injury may contribute to the anemia of chronic renal disease.

Cell Survival↗
PubMed1998

Correlation between lumbo-ventricular perfusion and MRI-CSF flow studies in idiopathic normal pressure hydrocephalus.

BACKGROUND: After the initial description of normal pressure hydrocephalus (NPH) and its clinical triad, there has been a continuous interest from clinicians and researchers to set different diagnostic criteria that would make the selection of candidates for shunt surgery easier and more precise. METHODS: A preliminary group of 12 patients was given a diagnosis of idiopathic normal pressure hydrocephalus by clinical and radiologic criteria. Each patient underwent two different tests: a magnetic resonance imaging-cerebrospinal fluid (MRI-CSF) flow study and a lumbo-ventricular perfusion test. The purpose was to compare the correlation of the results obtained with these tests and the clinical results obtained after CSF diversion. Eleven patients were given shunts and one was managed with lumbar punctures. RESULTS: One year after treatment, 10 of the 12 patients had improved with good results. The MRI-CSF flow studies were reliable in six patients; there were five false negatives and one false positive. The lumbo-ventricular perfusion test showed reliability in nine patients; there were two false negatives and one false positive. In only three patients were the results of both of these tests in accordance with the outcome. CONCLUSIONS: Even though there are few patients in this study so far, the data suggests that at the present time the most predictive guides for the diagnosis of NPH and its outcome after shunting are the clinical criteria and the radiological findings in computed tomography (CT) and/or MRI rather than lumbo-ventricular perfusion and CSF flow studies.

Adolescent↗
PubMed1998

Hemodialysis access failure: a call to action.

Recent evidence suggests that the cost as well as the morbidity associated with the maintenance of hemodialysis access is increasing rapidly; currently, the cost exceeds 1 billion dollars and access related hospitalization accounts for 25% of all hospital admissions in the U.S.A. This increase in cost and morbidity has been associated with several epidemiological trends that may contribute to access failure. These include late patient referral to nephrologists and surgeons, late planning of vascular access as well as a shift from A-V fistulaes to PTFE grafts and temporary catheters, which have a higher failure rate. The reasons for this shift in the types of access is multifactorial and is not explained by changes in the co-morbidities of patients presenting to dialysis. Surgical preference and training also appear to play an important role in the large regional variation and patency rate of these PTFE grafts. We propose a program for early placement of A-V fistulae, a continuous quality improvement, multidisciplinary program to monitor access outcome, the development of new biomaterials, and a research plan to investigate pharmacological intervention to reduce development of stenosis and clinical interventions to treat those that do develop, prior to thrombosis.

Arteriovenous Shunt, Surgical↗
PubMed1998

Results of linear accelerator-based radiosurgery for intracranial meningiomas.

OBJECTIVE: We report the outcomes of patients treated with linear accelerator-based radiosurgery for intracranial meningiomas at our institution. METHODS: We reviewed 127 patients with 155 meningiomas treated with stereotactic radiosurgery (SRS) at the study institutions between October 1988 and December 1995. RESULTS: There were 86 female and 41 male patients (median age, 61.5 yr; range, 19.9-87.9 yr). The median follow-up period was 31 months (range, 1.2-79.8 mo). The median tumor volume was 4.1 cc (range, 0.16-51.2 cc), and the median marginal dose was 15 Gy (range, 9-20 Gy). The tumor locations were as follows: convexity, 31 tumors; parasagittal/falcine, 39 tumors; cranial base, 82 tumors; and ventricular/pineal, 3 tumors. There were 106 benign, 26 atypical, and 18 malignant meningiomas and 5 cases of meningiomatosis. SRS was performed on 48 lesions as the initial treatment and on 107 lesions as adjunct therapy. Freedom from progression was observed in 107 patients (84.3%) at a median time of 22.9 months (range, 1.2-79.8 mo). Twenty patients (15.7%) had disease progression (16 marginal [12.6%] and 4 local [3.1%]) at a median time of 19.6 months (range, 4.1-69.3 mo); the median time for freedom from progression for the benign, atypical, and malignant meningiomas was 20.9, 24.4, and 13.9 months, respectively. Actuarial tumor control for the patients with benign meningiomas was 100, 92.9, 89.3, 89.3, and 89.3% at 1, 2, 3, 4, and 5 years, respectively. Six patients (4.7%) had permanent complications attributable to SRS (median time, 10.3 mo; range, 4.3-18.0 mo); 13 patients died as a result of causes related to the meningiomas (median, 17.5 mo; range, 4.3-37.3 mo). The 1-, 2-, 3-, 4-, and 5-year survival probability for the entire group of patients was 90.3, 82.6, 73.6, 70.5, and 68.2%, respectively; for patients with benign meningiomas, excluding death resulting from intercurrent disease, the survival probability was 97.6, 94.8, 91.0, 91.0, and 91.0%, respectively. The 1-, 2-, 3-, and 4-year survival probability for the patients with atypical and malignant meningiomas was 91.7, 83.3, 83.3, and 83.3% and 92.3, 64.6, 43.1, and 21.5%, respectively. CONCLUSION: Even though complications from SRS are expected more frequently with large tumors near critical structures, SRS is a safe and effective means of treating selected meningiomas.

Adult↗
PubMed1998

A multicenter comparison of dialysis membranes in the treatment of acute renal failure requiring dialysis.

The mortality of patients with acute renal failure (ARF) remains high, and in several large studies approaches 60%. This mortality is particularly high in patients with ARF who require dialysis and has not changed substantially over several years, despite the introduction of major advances in monitoring and treatment. Increasing prevalence of comorbidities has been suggested as the major factor in this persistently high mortality. This study investigates the potential role of the dialysis membrane on patient outcome in a prospective multicenter study of 153 patients with ARF requiring dialysis. The membrane assignment was made in alternating order and was limited to membranes with low complement activation (Biocompatible [BCM]) and cellulosic, high complement activation (Bioincompatible [BICM]). Both types of membranes were low-flux membranes. Patients were dialyzed with the assigned membrane until recovery, discharge from hospital, or death. The severity of illness of each patient was assessed using the APACHE II score at the time of initiation of dialysis. A logistic regression analysis was used to adjust for the APACHE II score. The results of the study showed a statistically significant difference in survival (57% in patients on BCM, 46% in patients on BICM; P = 0.03) and in recovery of renal function (64% in patients on BICM and 43% in patients on BICM; P = 0.001). These differences were particularly marked in the patients who were nonoliguric (>400 ml/d of urine output) at initiation of the study. In the subset of patients who were nonoliguric at the start of dialysis, a larger fraction (70%) became oliguric after initiating dialysis on a BICM membrane, in contrast to 44% who were initiated on a BCM membrane (P = 0.03). It is concluded that the biocompatibility of the dialysis membrane plays a role in the outcome of patients with ARF, particularly those who are nonoliguric at the time of initiation of dialysis.

APACHE↗
PubMed1997

Gangliogliomas in adults.

BACKGROUND: Gangliogliomas are rare tumors occurring in both children and adults that are characterized by the presence of neoplastic cells resembling both neurons and glia. METHODS: The authors reviewed 18 adults patients with intracranial gangliogliomas treated at the study institutions between October 1987 and November 1995. RESULTS: The median age at diagnosis was 33.7 years, with a range of 21 to 55 years. Median follow-up was 37.7 months, with a range of 4 months to 13 years. Clinical manifestations among the patients included seizures (13), headache (2), ataxia (1), and hemiparesis and paresthesias (1 patient each). Tumors were located in the temporal lobe (6 patients), temporal lobe and thalamus (1 patient), frontal lobe (5 patients), cerebellum (4 patients), and insula or thalamus (1 patient each). Thirteen patients underwent gross total resection, 4 underwent incomplete resection, and 1 underwent only a stereotactic biopsy. Treatment modalities included surgery only, surgery plus radiation, and surgery plus radiation and chemotherapy. Median survival was 90.3 months, with a range of 14 months to 13 years. Three patients were dead at follow-up with a mean survival of 32.3 months. These patients showed anaplastic features in their pathology at initial surgery or surgery for recurrence. CONCLUSIONS: In adults, gangliogliomas have a relatively favorable prognosis; however, the presence of anaplastic features predicts a worse outcome.

Adult↗
PubMed1997

Initial characterization of the dosimetry and radiology of a device for administering interstitial stereotactic radiosurgery.

OBJECTIVE: We report the design and initial characterization of the dosimetry and radiobiology of a novel device for interstitial stereotactic radiosurgery. INSTRUMENTATION: The device is lightweight, handheld, and battery-powered, and it emits x-ray radiation from the tip of a probe 3 mm in diameter by 10 cm in length. METHODS: The dosimetry was characterized by two independent methods: thermoluminescent dosimeters and radiochromic film. The radiobiology was characterized by in vivo irradiation of rat liver, dog liver, and dog brain. The animals were killed at varying intervals of time, and histological examinations were performed. Heat transfer from the probe to dog brain was studied in vivo by placing thermocouple sensors around the probe tip before irradiating. RESULTS: Both dosimetric methods showed a steep dose-distance fall-off relationship (proportional to the reciprocal of the cube of the distance from the probe tip). Rats and dogs that were killed weeks to months after liver irradiation tended to have sharply demarcated lesions. Liver enzyme levels, measured serially in the dogs, did not give evidence of chronic inflammation. Histological examination of the brains of dogs that were killed acutely after irradiation did not show evidence of inflammation, edema, or hemorrhage. The tissue temperature elevation 1 cm from the tip never exceeded 0.5 degree C, thereby excluding hyperthermia as a significant contributor to the formation of lesions. CONCLUSIONS: Because this device requires relatively few supporting resources, has sharp dosimetric properties, and seems to be safe, it may be useful as a clinical tool for interstitial stereotactic radiosurgery.

Animals↗
PubMed1996

In vitro differentiation of isolated stem cells from the midgut of Manduca sexta larvae

Isolated spherical stem cells from midguts of pharate fourth-instar larvae of Manduca sexta proliferated in vitro in the presence of 1 ng ml-1 20-hydroxyecdysone and co-cultured fat body tissue or cell-free fat body extract from M. sexta, Lymantria dispar or Heliothis virescens. In this environment, the stem cells were able to undergo mitosis and increase in number. However, stem cells were only able to differentiate to mature goblet and columnar cells when cell-free conditioned medium, taken from midgut cell cultures containing mature cells as well as stem cells and differentiating forms, was introduced into the culture medium. The presence of early and mature goblet cells, lying randomly on their sides, suggested that cell polarity developed in vitro as an intrinsic property of individual cells rather than with reference to an external inductive material. The differentiation factor (or factors) from the conditioned medium appears to include a heat-stable, peptide-like molecule of 10 kDa or less.

Journal Article↗