The pharmacokinetics of boron was studied in rats by administering a 1 ml oral dose of sodium tetraborate solution to several groups of rats (n=20) at eleven different dose levels ranging from 0 to 0.4 mg/100 g body weight as boron. Twenty-four-hour urine samples were collected after boron administration. After 24 h the average urinary recovery rate for this element was 99.6+/-7.9. The relationship between boron dose and excretion was linear (r=0.999) with a regression coefficient of 0.954. This result suggests that the oral bioavailability (F) of boron was complete. Another group of rats (n=10) was given a single oral injection of 2 ml of sodium tetraborate solution containing 0.4 mg of boron/100 g body wt. The serum decay of boron was followed and found to be monophasic. The data were interpreted according to a one-compartment open model. The appropriate pharmacokinetic parameters were estimated as follows: absorption half-life, t1/2a=0.608+/-0.432 h; elimination half-life, t1/2=4.64+/-1.19 h; volume of distribution, Vd = 142.0+/-30.2 ml/100 g body wt.; total clearance, Ctot=0.359+/-0.0285 ml/min per 100 g body wt. The maximum boron concentration in serum after administration (Cmax) was 2.13+/-0.270 mg/l, and the time needed to reach this maximum concentration (Tmax) was 1.76+/-0.887 h. Our results suggest that orally administered boric acid is rapidly and completely absorbed from the gastrointestinal tract into the blood stream. Boric acid in the intravascular space does not have a strong affinity to serum proteins, and rapidly diffuses to the extravascular space in proportion to blood flow without massive accumulation or binding in tissues. The main route of boron excretion from the body is via glomerular filtration. It may be inferred that there is partial tubular resorption at low plasma levels. The animal model is proposed as a useful tool to approach the problem of environmental or industrial exposure to boron or in cases of accidental acute boron intoxication.

Animals↗

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Serial IMP-SPECT and EEG studies in an infant with hemimegalencephaly.

An 8-month-old girl of hypomelanosis of Ito associated with hemimegalencephaly had frequent seizures beginning 44 h after birth. The seizures were secondarily generalized or unilateral initially, followed by infantile spasms at about 1.5 months of age. Frequent partial seizures appeared at 4 months of age. [123I]N-Isopropyl-p-iodoamphetamine (IMP) single photon emission computed tomography (SPECT) was performed serially during an interictal period at 1, 3 and 7 months of age. At 1 and 3 months, IMP-SPECT showed a marked increase of IMP uptake in the pathological left hemisphere and electroencephalography (EEG) revealed left-sided dominant hypsarrhythmia. At 7 months of age, a reversal was seen, there being decreased uptake on SPECT in the pathological hemisphere and abundant high amplitude background activity mingled with epileptic discharges on EEG in the non-pathological hemisphere. These serial changes of IMP uptake on SPECT seemed to reflect either changes in epileptic activity or maturational changes in cerebral perfusion in hemimegalencephaly.

Age Factors↗

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Xeroderma pigmentosum with versive seizures.

A boy with group A xeroderma pigmentosum and a series of progressive neurologic complications developed versive seizures at 8 years of age. Electroencephalography at 6 years of age revealed no epileptic changes or focal abnormalities. He was seizure-free until versive seizures developed; electroencephalography revealed frequent spike discharges in the right central and temporal regions. Neurologic complications and electroencephalographic abnormalities of 34 patients with group A xeroderma pigmentosum also were assessed. Only 3 patients with xeroderma pigmentosum have been reported to have a seizure disorder. This patient is the fourth reported with group A xeroderma pigmentosum associated with a convulsive disorder. Although neurologic manifestations in group A xeroderma pigmentosum are progressive and severe, it is unknown why so few of these patients develop seizure disorders.

Brain↗

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Aicardi syndrome associated with an embryonal carcinoma.

A Japanese girl is reported who had the typical clinical features of Aicardi syndrome associated with embryonal carcinoma. She developed infantile spasms at approximately 4 weeks of age; her seizures were intractable in spite of treatment with numerous antiepileptic drugs and ACTH. At 22 months of age, her left cheek gradually became swollen. Laboratory findings were normal except for a marked increase in serum alpha-fetoprotein. A transoral biopsy of the tumor revealed an embryonal carcinoma. This patient is the first reported with Aicardi syndrome and embryonal carcinoma. The relationship between congenital malformations and neoplasms is discussed.

Agenesis of Corpus Callosum↗

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Dandy-Walker cyst associated with occipital meningocele.

Dandy-Walker cyst associated with occipital meningocele is very rare. Only 12 patients have been reported. We report a female infant with Dandy-Walker cyst and occipital meningocele whose diagnosis was suspected antenatally by in utero ultrasonography. At birth, head circumference was normal for 37 weeks gestation. She underwent surgical repair of the occipital meningocele immediately after birth. The post-operative course was uneventful until the sixth day of life when progressive enlargement of the head with progressive ventricular dilatation was recognized. Communication between the posterior fossa cyst and the occipital meningocele was confirmed neuroradiologically; the occipital meningocele may have compensated for the increased intracranial pressure in fetal life.

Dandy-Walker Syndrome↗

PubMedDate not supplied

Internal carotid arterial blood flow velocity in infants.

The differences in the velocity and pulsatility indexes in the internal carotid artery were evaluated in 62 normal controls, 42 infants with cerebral palsy, and 22 infants with mental retardation, all within the first year of life. In the normal controls, the average maximal blood flow velocity (A/L), and the maximal end-diastolic flow velocity increased during the first year of life. Pulsatility index decreased significantly between the ages of newborn to 2 mos and 3-5 mos, and remained constant thereafter. Compared with normal controls, the average maximal blood flow velocity and the maximal end-diastolic flow velocity values were significantly reduced in infants with cerebral palsy during the first 6 months of life, while no differences in these values were observed in infants with mental retardation. There were no differences in the pulsatility index values in the 3 subject groups throughout the first year of life. Flow velocity in the internal carotid artery could reflect the status of the cerebral circulation in infants within the first year of life.

Blood Flow Velocity↗

PubMedDate not supplied

Role of angiotensin II receptors in the regulation of vasomotor neurons in the ventrolateral medulla.

1. There is a high density of angiotensin type 1 (AT1) receptors in various brain regions involved in cardiovascular regulation. The present review will focus on the role of AT1 receptors in regulating the activity of sympathetic premotor neurons in the rostral part of the ventrolateral medulla (VLM), which are known to play a pivotal role in the tonic and phasic regulation of sympathetic vasomotor activity and arterial pressure. 2. Microinjection of angiotensin (Ang) II into the rostral VLM (RVLM) results in an increase in arterial pressure and sympathetic vasomotor activity. These effects are blocked by prior application of losartan, a selective AT1 receptor antagonist, indicating that they are mediated by AT1 receptors. However, microinjection of AngII into the RVLM has no detectable effect on respiratory activity, indicating that AT1 receptors are selectively or even exclusively associated with vasomotor neurons in this region. 3. Under normal conditions in anaesthetized animals, AT1 receptors do not appear to contribute significantly to the generation of resting tonic activity in RVLM sympathoexcitatory neurons. However, recent studies suggest that they contribute significantly to the tonic activity of these neurons under certain conditions, such as salt deprivation or heart failure, or in spontaneously hypertensive or genetically modified rats in which the endogenous levels of AngII are increased or in which AT1 receptors are upregulated. 4. Recent evidence also indicates that AT1 receptors play an important role in mediating phasic excitatory inputs to RVLM sympathoexcitatory neurons in response to activation of some neurons within the hypothalamic paraventricular nucleus. The physiological conditions that lead to activation of these AT1 receptor-mediated inputs are unknown. Further studies are also required to determine the cellular mechanisms of action of AngII in the RVLM and its interactions with other neurotransmitters in that region.

Angiotensin II↗

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Bilateral occlusions in the cervical portion of the internal carotid arteries in a child.

An 8-year-old boy with a history of recurrent tonsillitis and cervical lymphadenopathy developed acute hemiplegia. Cerebral angiography revealed bilateral occlusions of the cervical portion of the internal carotid arteries. Cerebral arterial occlusion in childhood has been attributed to many causes, e.g., trauma and infections of the neck. In the present case, though not clearly proved, inflammatory processes may have been related to the occlusion.

Arterial Occlusive Diseases↗

PubMedDate not supplied

Regional cerebral blood flow, clinical manifestations, and age in children with moyamoya disease.

In children with Moyamoya disease, transient ischemic attacks often occur during hyperventilation, and the frequency of attacks usually decreases with advancing age. To elucidate the mechanism of the attacks, the regional cerebral blood flow was measured during rest and/or hyperventilation in children aged 3-16 with Moyamoya disease. Regional cerebral blood flow during rest was significantly higher in younger children with Moyamoya disease, and it progressively decreased with advancing age through childhood. During hyperventilation, regional cerebral blood flow decreased in all the children, although blood flow in younger children was still higher than that in the older children. Nevertheless, transient ischemic attacks were more readily precipitated by hyperventilation in the younger than in the older children. Cerebral metabolic demand is much higher in the first decade of life than in later decades. Therefore, it seems likely that even a moderate reduction in cerebral blood flow can cause metabolic impairment in young children. Such high cerebral metabolic demand may play an important role in the frequent occurrence of transient ischemic attacks in young children with Moyamoya disease.

Aging↗