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Biomedical subjects

J Whyte

Publications and source records attributed to J Whyte.

96 records · Page 6Linked to original sources
PubMedDate not supplied

Effects of methylphenidate on attentional function after traumatic brain injury. A randomized, placebo-controlled trial.

Attention deficits after traumatic brain injury (TBI) are common and disabling. Many pharmacologic agents have been used to ameliorate attention deficits, and considerable interest has focused on methylphenidate (MP) because of its documented efficacy in attention deficit disorder. However, clinical studies of MP in subjects with TBI have yielded mixed results. We examined the effects of MP on attentional function in individuals with TBI referred specifically for attentional assessment and treatment. Subjects were studied in a double-blind, placebo-controlled, repeated crossover design, using five different tasks designed to measure various facets of attentional function. MP produced a significant improvement in the speed of mental processing. Orienting to distractions, most aspects of sustained attention, and measures of motor speed were unaffected. These results suggest that MP may be a useful treatment in TBI but is primarily useful for symptoms that can be attributed to slowed mental processing.

Adolescent↗
PubMedDate not supplied

Carbamazepine replacement of phenytoin, phenobarbital and primidone in a rehabilitation setting: effects on seizure control.

Most patients who receive anticonvulsants after traumatic brain injury are treated with the sedative anticonvulsants phenytoin and/or phenobarbital, or perhaps primidone. However, there is considerable evidence demonstrating that these medications have a deleterious effect on cognitive function. Thus, in a rehabilitation setting, alternatives should be sought. Carbamazepine has been found to be relatively free of such effects, and would be an optimum alternative if seizure control were comparable. We have studied the effects of withdrawing phenytoin, phenobarbital and primidone, and using carbamazepine as the primary anticonvulsant in 27 patients at the Greenery Rehabilitation and Skilled Nursing Center for whom ongoing anticonvulsant treatment was considered to be necessary due to previous seizures or a high risk of the occurrence of seizure. We compared a 3 month baseline period (just prior to carbamazepine introduction or sedative anticonvulsant tapering), to a 3 month post-withdrawal period immediately following sedative anticonvulsant withdrawal, when carbamazepine was the sole anticonvulsant. In 20 out of 21 patients in whom carbamazepine replaced sedative anticonvulsants seizure control was essentially similar or somewhat improved. In only one patient did the substitution with carbamazepine result in a loss of seizure control. Six patients were initially receiving carbamazepine in combination with phenytoin and/or phenobarbital. The removal of phenytoin and phenobarbital, leaving carbamazepine as sole therapy, resulted in improved seizure control in three patients and no change in the other three. In the light of carbamazepine's reportedly less detrimental effects on cognitive function and behaviour in other patient populations, it should perhaps be considered as a first line anticonvulsant, especially for patients in rehabilitation settings.

Adult↗
PubMedDate not supplied

The vasectomized testis.

We have performed a qualitative study on effects of vasectomy on the testicular structure. Vasectomy performed with the traditional technique changes testicular structure. At first, the injuries are slight and restricted, but gradually, and in a time-dependent manner, become more severe and extensive. Ultrastructure studies indicate that the spermatogonia and Sertoli's cells are the most resistant to vasectomy, and are even observed in some regenerating testes lacking a complete germinal epithelium. Morphometric studies revealed a decrease in epithelial depth, an increase in the thickness of the basement membrane and in surface of the interstitial space, all significant (P < 0.01) with respect to the control. However, the percentage of the interstitial tissue occupied by cells, did not show any significant difference. We propose that the increase of intraluminal pressure is the essential factor that provokes testicular atrophy.

Animals↗
PubMedDate not supplied

[Structural peculiarities of the human cerebral communicating arteries and their repercussion in encephalic vascular pathology].

INTRODUCTION: The cerebrovascular accidents are one of the most frequent causes of morbimortality. Most of them are caused for the break of aneurysms in communicating arteries. The weak structure of these vessels explain the reason of these accidents. OBJECTIVE: The reason of this paper is study the organization of communicating arteries as cause of this fragility. Material and methods. The material of this study is composed of 61 human cerebral communicating arteries, grouped in decades. The study has been carried out by histological routine. RESULTS: In general the structure of cerebral communicating arteries is characterized for the thinness and irregularity of the wall. In the childhood the internal elastic membrane and tunica media show thicker, while in young and adult people appear elastic fibers and reticulin as well as smooth muscle cells in tunica media. In adulthood (50 60 years) collagen in adventicia occupies tunica media, and adventicia is weaked. There are frequent media defects in these communicating arteries, that are usually repaired for conjunctive tissue stopper with abundance of collagen fibers. Starting from 4th decade the internal elastic membrane shows a great number of fenestrae through muscle and fiber tissue of media occupying subintimal space. Doubtless media defects mean the most severe threat of vascular outbreak. CONCLUSION: The structural evolution with the age of communicating arteries, with predominance of collagen over elastin and reticulin, could be their reason of fragility.

Adult↗
PubMedDate not supplied

Arterial microanastomosis technique by using only one stitch.

The starting point of this work is the description of a microsurgical technique designed to carry out termino-terminal arterial anastomosis in rats. The technique is based on the intussusception of the afferent vessel of the anastomosis in the efferent vessel, both of which are fixed by a horizontal U-shaped stitch. Of the twelve cases which make up this series, haemorrhage appeared in two, and a postanastomotic aneurysm developed in one. The lack of complications both before and after operating, even in the long term, in the balance of the cases (75%), together with the simple and quick procedure of this kind of anastomosis, makes this technique a possible alternative to the classical techniques of vascular microanastomosis in experimental surgery.

Anastomosis, Surgical↗