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Biomedical subjects

L Blake

Publications and source records attributed to L Blake.

At least 19 recordsLinked to original sources
PubMed1996

Changes in the heavy metal contents of soil from the Park Grass Experiment at Rothamsted Experimental Station.

The classical Rothamsted Experiments allow to contribute to current research. The heavy metal content of soil and hay samples have been measured with ICP-AES from a control and a fertilized plot of the Park Grass Experiment. Today a difference of 1.2 can be observed in the pH levels of the control and fertilized plots; the pH level of the control plot has decreased about 1.0, that of the fertilized plot about 2.2 as a result of 150 years of acid deposition and fertilization. The changes in the pH levels has caused many changes in the heavy metal content of the top layer of the soil. Using different extraction methods (e.g., ammonium acetate, EDTA, and sequential analysis), the heavy metal content of different fractions have been estimated. In the control plot, the Zn, Cd and Pb content increased. In the fertilized plot, the Pb and Cd contents have also increased because of atmospheric deposition and small amounts of lead in the fertilizer. The available form of Cd and Pb increased in both the control and the fertilized plots.

Journal Article↗
PubMed1996

Assessment of hemodynamic effects of angiotensin-converting enzyme inhibitor therapy in chronic aortic regurgitation by using velocity-encoded cine magnetic resonance imaging.

Long-term treatment with angiotensin-converting enzyme (ACE) inhibitors has beneficial effects in patients with chronic aortic regurgitation by reducing left ventricular volumes and regurgitant fraction. Velocity-encoded cine magnetic resonance imaging can directly measure antegrade (forward stroke volume) and retrograde blood flow (regurgitant volume) in the ascending aorta. Velocity-encoded cine magnetic resonance imaging was used in 9 patients with moderate to severe aortic regurgitation (regurgitant fraction 49% +/- 17%) to measure regurgitant fraction, regurgitant volume, and forward stroke volume at baseline and 3 months after therapy with enalapril (mean dose 29 +/- 13 mg). Ten additional patients with aortic regurgitation without any drug therapy served as a control group. In the treatment group, systolic blood pressure slightly decreased from 132 +/- 20 mm Hg to 121 +/- 14 mm Hg (p = not significant), whereas diastolic blood pressure and heart rate (beats per minute) remained unchanged. Regurgitant fraction decreased in 6 patients (responders) from 49% +/- 19% to 39% +/- 20% (percentage change 24% +/- 14%, p = 0.002) and was unchanged in 3 patients (nonresponder, 49% +/- 19% vs 51% +/- 16%; p = not significant). In the responder group, forward stroke volume increased from 128 +/- 32 ml to 148 +/- 57 ml, whereas regurgitant volume remained unchanged (67 +/- 40 ml vs 65 +/- 51 ml). At baseline, the responder group had a significant higher total vascular resistance than the nonresponder group (998 +/- 538 dyne.sec.cm-5 vs 625 +/- 214 dyne.sec.cm-5; p < 0.05). With enalapril treatment, total vascular resistance in the responder group tended to decrease (891 +/- 576 dyne.sec.cm-5), but slightly increased in the nonresponder group (679 +/- 276 dyne.sec.cm-5). The control group showed no changes in regurgitant fraction, regurgitant volume, forward stroke volume, and total vascular resistance at follow-up.

Adult↗
PubMed1996

Magnetic resonance neurography of peripheral nerve lesions in the lower extremity.

OBJECTIVE: We describe the clinical application and utility of high-resolution magnetic resonance neurography (MRN) techniques to image the normal fascicular structure of peripheral nerves and its distortion by mass lesions or trauma in the lower extremity. METHODS: MRN images were obtained using a standard 1.5 Tesla magnet and custom built phased-array coils. Patients were imaged using T1-weighted spin echo without and with gadolinium, T2-weighted fast spin echo with fat peripheral nerve tumors (three neurofibromas and one schwannoma), two with intraneural cysts, and three with traumatic peripheral nerve lesions. Six patients with peripheral nerve mass lesions underwent surgery, thereby allowing MRN images to be correlated with intraoperative and pathological findings. RESULTS: Preoperative MRN accurately imaged the normal fascicular anatomy of peripheral nerves and precisely depicted its relation to tumor and cystic lesions. Increased signal on T2-weighted fast spin-echo and short tau inversion recovery fast spin-echo pulse sequences was seen in the peripheral nerve fascicles of patients with clinical and electrodiagnostic evidence of nerve injury. CONCLUSION: MRN proved useful in the preoperative evaluation and planning of surgery in patients with peripheral nerve lesions.

Adult↗
PubMed1994

Depot antipsychotic drugs. Place in therapy.

The pharmacokinetics of depot antipsychotic medications are such that an intramuscular injection given at intervals of from 1 to 4 weeks will produce adequate plasma concentrations that are sufficient to prevent relapse over the dosage interval. Such medication is useful in patients who do not reliably take their oral medication. The pharmacokinetics and clinical actions of various depot formulations of antipsychotic drugs have been extensively studied. Unfortunately, patients who do not reliably take their oral medications are unlikely to volunteer for controlled studies. This is because the same factors that influence a patient to not cooperate with the physician in taking the medication as prescribed will also interfere with their willingness to volunteer for research protocols. Thus, evidence from blinded controlled trials may not necessarily reflect the actual patient population at risk. We feel that particularly important evidence of efficacy of depot vs oral medication comes from mirror-image studies. In these trials, the number of hospitalisations after initiation of depot medication is compared with that observed when the patient was solely taking oral medication. Studies of this type show that depot medication substantially reduces the rate of relapse. There is considerable evidence about how long depot medications should be used. For many patients, depot medication to prevent relapse in schizophrenia should be used for the life of the patient. As the conventional antipsychotic agents are replaced by a new generation of agents, the need for depot formulations will continue, and the knowledge gained about the current formulations should transfer to future generations of drugs.

Antipsychotic Agents↗
PubMed1994

Informed consent.

Informed consent is an issue preoccupying many in both the legal and medical professions. The author looks at what it means in the day-to-day clinical situation.

Ethics, Medical↗
PubMed1994

Do electrolyte-containing beverages improve water imbalance in hyponatremic schizophrenics?

BACKGROUND: To determine if ready access to a sodium-containing beverage ameliorates life-threatening water imbalance, we compared Gatorade to water in an ABA design. METHOD: Four male chronic schizophrenic inpatients with symptomatic hyponatremia drank water for 1 week, Gatorade plus water for 3 weeks, and then water again for 1 week. Afternoon plasma osmolality and morning serum sodium levels were used to estimate hydration status, and morning and afternoon urine creatinine concentrations were used to estimate fluid intake. RESULTS: During the baseline phase, subjects were mildly polydipsic and mildly overhydrated in the morning and severely overhydrated in the afternoon. All subjects stated they preferred Gatorade and appeared to consume large quantities of it. Indices of fluid intake and hydration status did not differ between the two control phases, nor between the treatment phase and the other two phases. Frequency of severe hypo-osmolemia was also unaffected. CONCLUSION: Substitution of electrolyte-containing beverages is not likely to prevent water intoxication.

Adult↗
PubMed1994

Extraskeletal myxoid chondrosarcoma: an unusual tumour in a 6-year-old boy.

Extraskeletal (soft-tissue) myxoid chondrosarcoma is an uncommon malignant tumour that usually develops in the fifth, sixth or seventh decade of life. The authors describe its occurrence in a 6-year-old boy. Histologically, the tumour must be differentiated from parachordoma and epithelioid hemangioendothelioma, with which it shares some features.

Child↗
PubMed1993

Association of nonsuppression of cortisol on the DST with primary polydipsia in chronic schizophrenia.

Thirteen polydipsic and 40 nonpolydipsic chronic schizophrenic patients received the dexamethasone suppression test while stabilized on psychotropic medication regimens. Thirty-eight percent (N = 5) of those with polydipsia but only 5% (N = 2) of those without polydipsia were nonsuppressors of cortisol (i.e., had an abnormal response). It is suggested that hippocampal dysfunction could cause both polydipsia and cortisol dysregulation in these patients.

Adolescent↗
PubMed1992

Failure of a binaural comprehension deficit to select responders to earplug use in schizophrenia.

Previous studies have suggested that on the Auditory Comprehension Test, a significant proportion of schizophrenics demonstrate a binaural comprehension deficit. To test whether wearing an earplug in their more poorly performing ear would be beneficial, we studied 34 in-patient schizophrenics and noted a binaural deficit in 12 (35%). Of these, eight patients subsequently wore an earplug in each ear for at least one week. We found no effect of the earplug on psychopathology.

Adult↗
PubMed1977

Pattern discrimination thresholds after partial inferior temporal or lateral striate lesions in monkeys.

Ablation of inferior temporal (IT) cortex, particularly of the posterior region, produces severe impairment in pattern discrimination learning. The present study examined whether this impairment is associated with raised pattern discrimination thresholds. Groups of three monkeys each were given either anterior IT, posterior IT, or foveal striate lesions, or kept as controls. They were trained after surgery on a threshold task in which a 90 degrees white angle on a gray ground was the standard, and 15 angles ranging from 10 degrees through 88.5 degrees were the comparisons. As expected, monkeys with posterior IT lesions were the most severely impaired in learning the initial discrimination (90 degrees vs. 10 degrees). However, only the monkeys with foveal striate lesions showed significant impairment on the subsequent threshold determinations. The results indicate that raised pattern discrimination thresholds are not the cause of the pattern discrimination learning deficits produced by inferior temporal lesions. Data from additional visual discriminations presented after threshold testing was completed point, instead, to a loss of attention to stimulus features as the explanation for the learning deficit.

Animals↗