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Biomedical subjects

M Brock

Publications and source records attributed to M Brock.

At least 163 records · Page 9Linked to original sources
PubMed1982

Roles of subarachnoid blood clots and norepinephrine in cerebral vasospasm.

The content of norepinephrine (NE) in the ventricular, basal cisternal and lumbar cerebrospinal fluid (CSF) was determined in 19 patients with ruptured cerebral aneurysms. The cisternal CSF in patients with vasospasm contained a significantly higher level of NE (0.246 +/- 0.0490 ng/ml) compared with those without vasospasm (0.075 +/- 0.001 ng/ml) (p less than 0.001). However, this increase is not considered to be high enough to constrict cerebral arteries, unless there is an increased NE-sensitivity in subarachnoid haemorrhage. Vascular responses to NE in vivo were then studied after reversing blood-induced prolonged vasospasm of the rabbit's basilar artery through a transclival approach as well as a newly developed basal cisternal irrigation model. However, NE in molar concentrations between 1 x 10(-10) and 10(-2) failed to produce further contraction of the artery. In conclusion, the increase in NE with vasospasm might be only a secondary phenomenon, and not a causative factor of vasospasm. Early removal of subarachnoid blood clots seemed to prevent the development of vasospasm.

Animals↗
PubMed1982

The determination of brain water content: microgravimetry versus drying-weighing method.

The microgravimetric technique and the drying-weighing method for the determination of brain water content are analyzed and compared. A new method has been devised for the automatic production of the gradient column. For gravimetry, tissue samples weighing more than 30 mg have proven adequate for measurement. Specific gravity (SG) should be determined as early as 1 minute after tissue is inserted into the gradient column. Calculations of cerebral blood volume (CBV) from changes in SG of both brain tissue and intravascular perfusate have shown that the SG of brain tissue is considerably influenced by changes in CBV. This is because the SG of blood is higher than that of brain tissue, and may lead to a decrease of SG of about 0.002 in anemic cortex and of 0.001 in anemic white matter, which will simulate a false increase in tissue volume as water of 4% and 2%, respectively. This methodological error may be relevant when the early stages of ischemic brain edema development are studied. Water content of brain tissue can also be determined with acceptable accuracy by vacuum freeze-drying samples of brain tissue weighing about 100 mg. In contrast to cortex, white matter shows a wide range of individual and regional differences in water content. Thus, conclusions on the presence of brain edema drawn from tissue water determinations should always be subjected to cautious analysis and criticism.

Animals↗
PubMed1981

Endoscopic section of the sensory trigeminal root, the glossopharyngeal nerve, and the cranial part of the vagus for intractable facial pain caused by upper jaw carcinoma.

In a patient with intractable facial pain caused by a deep-seated carcinoma of the upper jaw, relief was obtained following endoscopic section of the sensory trigeminal root, the glossopharyngeal nerve, and the cranial part of the vagus. Previous stereotactic thalamotomy had failed. The endoscopic method is briefly described and discussed.

Cerebellopontine Angle↗
PubMed1981

Relationship between brain tissue pressure gradients and cerebral blood flow distribution studied in circumscribed vasogenic cerebral oedema.

The present experimental study was designed to examine the correlations between brain tissue pressures, pressure gradients and cerebral blood flow distribution associated with circumscribed cerebral vasogenic oedema. Following unilateral hemispheric cryogenic injury in 42 adult cats, brain tissue pressures increased as a function of time. Interhemispheric pressure gradients became most marked one hour after the cryogenic injury (3.9 mm Hg on average), gradually decreasing thereafter. Transtentorial pressure gradients developed within the first hour after the injury, and remained above 10 mm Hg. The dye injected into one carotid system by the "single dye passage" technique was redirected towards the contralateral hemisphere and also towards the subtentorial compartment, as brain tissue pressures increased. The shift in the flow-distribution of dye and blood was more pronounced in the posterior fossa structures. When intracranial tissue pressures exceeded 60 mm Hg almost no dye entered the cranial cavity. This accompanied the marked decrease in cerebral perfusion pressure.

Animals↗
PubMed1981

[Fundamental problems and improved methods in the measurement of specific gravity of cerebral tissues. (author's transl)].

Gravimetric determination of brain tissue water content through the measurement of specific gravity (SG) still poses some basic problems. We have studied some of them with the aid of a new gradient column. Using a specially designed conical cylinder to distribute the solution in a graded manner, and a floating apparatus, a gradient column was automatically prepared with a high linearity (r greater than 0.99990). Analysis of equilibration time-course curves of cat brain tissue fragments with various sizes showed that it was more accurate to use volumes as large as 50 mg, and to measure as early as one minute after tissue insertion. In normal brain, SG of grey matter was usually higher than that of white matter. In contrast, in a brain with oligemia or with low hemoglobin contents of blood, this relationship was reversed. Thus, SG can be influenced not only by water content, but also by other factors. As SG of blood is higher than that of brain tissue, cerebral blood volume (CBV) is of particular interest. Assuming the total brain volume as equal to 1, CBV and volume of brain proper excluding intravascular blood can be expressed as x and 1-x respectively. In a given brain tissue, SG of blood or perfusate a, and SG of whole brain tissue A can be measured. If SG of brain proper is expressed as y, the following equation can be introduced: ax + y(1-x)=A. If a and A are obtained from two different brains under the condition of constant CBV, x, 1-x and y can be calculated. For this purpose, values from normal brain and those from perfused brain with isotonic saline were applied. The calculated CBV was 7% in the grey and 3% in the white. SG of brain proper was as low as 0.002 in the grey and 0.001 in the white as compared to that of whole brain tissue. When these values are applied to the equation of percent change in tissue volume as water = (SG of control tissue-1)-(SG of experimental tissue-1)/(SG of experimental tissue-1) x 100%, the false positive increase of water in a completely ischemic brain without edema is approximately 4% in the grey and 2% in the white. Then, care should be taken in the assessment of water increase from SG, particularly in the early stage of ischemic edema.

Animals↗
PubMed1980

Intercarotid anastomosis with a vein graft in the rat. A model for microsurgical training.

The common carotid arteries were anastomosed through a venous graft in a group of ten rats. The right common carotid artery was ligated below and the left above the anastomosis. In a control group both common carotid arteries (CCA) were ligated. While the animals of the experimental group survived without neurological deficit, those in the control group died 2 hours to 11 days after operation. The anastomoses and brains were studied by light microscopy. The model described is convenient for practising microsurgery, and should constitute part of the routine training program of young neurosurgeons.

Animals↗
PubMed1978

The small frontolateral approach for the microsurgical treatment of intracranial aneurysms.

The authors describe a new approach (the Small Frontolateral Approach) for the elective microsurgical treatment of aneurysms of the rostral part of the circle of Willis, including those arising from the carotid siphon. This approach provides the advantage of permitting an easy, direct and "protective" attack to such aneurysms through a small and merely osteoplastic craniotomy.

Carotid Arteries↗
PubMed1978

[Measurement of ventricular fluid pressure and brain tissue pressure in acute experimental communicating hydrocephalus (author's transl)].

Malabsorption of cerebrospinal fluid was made experimentally by the administration of neutral carbon black suspension into the lateral ventricles of 22 adult cats. The compartmental analysis of intracranial pressure at the intraventricular fluid and tissue pressure in the cerebral white matter was carried out in the early stage of the communicating hydrocephalus. Following results were obtained: 1) Cerebrospinal fluid pressure from the lateral ventricle was always significantly higher than that from the brain tissue during the process of ventricular expansion. 2) Water content in the cerebral white matter was correspondingly increased when the pressure difference with greater value in ventricular fluid pressure was maintained. However tissue water content was decreased definitively when such pressure values at two compartments were equalized due to augment of the tissue pressure component. 3) Decreasing of cerebral blood flow demonstrated in spite of relatively higher value of cerebral perfusion pressure. From these findings the authors speculated that a higher pressure in the ventricular system will be a driving force, by which the enlargement of ventricular system was induced.

Animals↗
PubMed1977

Renography as a prognostic index of urinary tract problems in childhood.

Many radiological methods are used in investigating urinary tract problems in children, and some are poorly tolerated. The simplest and most acceptable technique is isotope renography. Its value has been assessed in predicting the outcome of urinary tract problems in 91 children over the age of 2 years presenting consecutively over a period of 3 months. The results of initial assessment by renography and radiography have been compared with the final clinical assessment 7 years later. 35 patients were identified as being "at risk" and all of these had abnormal renograms and radiograms. Normal renographys was found unexpectedly in some patients with severe reflux but with a good final result. It is concluded that renography can be used to screen children with urinary tract infection, thereby excluding the less acceptable radiological investigations unless the renogram is abnormal.

Child, Preschool↗
PubMed1977

Xeroradiography in assessment of the rheumatoid hand.

Comparable conventional x-rays had xeroradiographs were obtained of the hands of 22 patients with rheumatoid arthritis. Each metacarpophalangeal and proximal interphalangeal joint was scored for juxta-articular osteoporosis, erosions, loss of joint space, soft tissue thickening, joint deformity, and osteophytes on a 0-3 scale. For 10 hands the films were reported again after 3 months, and each technique was reproducible. Comparison between the 2 radiographic techniques showed that overall they gave similar results, although osteoporosis was reported more frequently on conventional x-rays, and loss of joint space and synovial thickening on xeroradiographs.

Arthritis, Rheumatoid↗
PubMed1977

[Clinical signs and therapy of intermittent normotensive hydrocephalus (author's transl)].

Ventricular fluid pressure (VFP) has been continuously recorded for several days in a series of 9 patients with Intermittently Normotensive Hydrocephalus. This entity can be diagnosed with a reasonable degree of certainty by this method, due to the occurrence of periodic increases of VFP--mainly of ramp-waves as described in the paper. Thus, the designation Intermittently Normotensive Hydrocephalus appears to be more exact. Therapy by means of CSF-shunting procedures is more successful in cases with clearcut periodic rises in VFP.

Adult↗