Adaptation to life on land at high O2 via transition from ferredoxin-to NADH-dependent redox balance.

Pyruvate : ferredoxin oxidoreductase (PFO) and iron only hydrogenase ([Fe]-HYD) are common enzymes among eukaryotic microbes that inhabit anaerobic niches. Their function is to maintain redox balance by donating electrons from food oxidation via ferredoxin (Fd) to protons, generating H2 as a waste product. Operating in series, they constitute a soluble electron transport chain of one-electron transfers between FeS clusters. They fulfil the same function-redox balance-served by two electron-transfers in the NADH- and O2-dependent respiratory chains of mitochondria. Although they possess O2-sensitive FeS clusters, PFO, Fd and [Fe]-HYD are also present among numerous algae that produce O2. The evolutionary persistence of these enzymes among eukaryotic aerobes is traditionally explained as adaptation to facultative anaerobic growth. Here, we show that algae express enzymes of anaerobic energy metabolism at ambient O2 levels (21% v/v), Chlamydomonas reinhardtii expresses them with diurnal regulation. High O2 environments arose on Earth only approximately 450 million years ago. Gene presence/absence and gene expression data indicate that during the transition to high O2 environments and terrestrialization, diverse algal lineages retained enzymes of Fd-dependent one-electron-based redox balance, while the land plant and land animal lineages underwent irreversible specialization to redox balance involving the O2-insensitive two-electron carrier NADH.

Neuroprotection by the NMDA receptor-associated open-channel blocker memantine in a photothrombotic model of cerebral focal ischemia in neonatal rat.

Excessive accumulation of glutamate or other excitatory amino acids and the subsequent overactivity of NMDA receptors is currently thought to lead to neuronal injury in cerebral ischemia. Therefore, antagonists of the NMDA receptor may offer an approach for the treatment of ischemic brain injury. Dizocilpine (MK-801), an NMDA receptor-associated channel blocker, protects neurons in several rodent stroke models. However, this drug has numerous side effects and causes apoptosis of neonatal neurons. Recently, another NMDA receptor-associated channel blocker, memantine, has been shown to ameliorate NMDA-receptor mediated neurotoxicity in neuronal cell cultures and in focal cerebral ischemia models in adult rats without substantial side effects. Memantine has been used clinically in the treatment of Parkinson's disease and spasticity for a number of years. Here we tested the effects of memantine on focal stroke caused by photochemical thrombosis in neonatal rats and demonstrated a neuroprotective effect of memantine in this model. We also found excellent correlation between infarct size determined by magnetic resonance imaging (MRI) and histopathological analysis in the same animals. A single pre-ischemic dose of memantine (20 mg/kg) given 15 min prior to induction of stroke reduced the infarct size by 36.3% when compared to control animals treated with normal saline (P < 0.0001). At this dosage, memantine manifests few, if any, neurobehavioral side effects. Thus memantine appears to be both safe and effective in neonatal as well as adult animal models of stroke.

Hypertensive encephalopathy as a complication of hyperdynamic therapy for vasospasm: report of two cases.

OBJECTIVE AND IMPORTANCE: After developing subarachnoid hemorrhage, patients may deteriorate from a variety of well-known causes, including rebleeding, hydrocephalus, and vasospasm. Many patients now undergo empirical hyperdynamic vasospasm therapy with hypervolemia, induced hypertension, and nimodipine. CLINICAL PRESENTATION: We report two cases of iatrogenic hypertensive encephalopathy occurring during hyperdynamic therapy for cerebral vasospasm after subarachnoid hemorrhage. Hypertensive encephalopathy is a syndrome of rapidly evolving generalized or focal cerebral symptoms occurring in the setting of severe hypertension, which is reversible with antihypertensive therapy. INTERVENTION: The syndrome can be diagnosed in the appropriate clinical setting with computed tomographic or magnetic resonance imaging that demonstrates characteristic findings. In both cases, decreasing the blood pressure resulted in neurological improvement. CONCLUSION: In the setting of induced hypertensive/hypervolemic therapy for vasospasm, hypertensive encephalopathy should be considered as a potentially reversible cause of delayed neurological decline.

De novo Chiari-I malformation in infants demonstrated by sequential magnetic resonance imaging scans. Report of two cases.

In this report we demonstrate the de novo development of Chiari-I malformation with hydrosyringomyelia in 2 toddlers on serial brain magnetic resonance imaging scans. We speculate that a mismatch in bony and neural development is the underlying mechanism of these de novo Chiari malformations.

Spinal subdural abscess: successful treatment with limited drainage and antibiotics in a patient with AIDS.

The authors present a case of Staphylococcus aureus spinal subdural abscess in a patient with AIDS. Although complete surgical drainage has been strongly advocated in the literature, this patient made a complete neurologic and symptomatic recovery and radiographically demonstrated resolution of the abscess with only limited surgical drainage and parenteral antibiotics. Magnetic resonance imaging findings of this unusual lesion are discussed. Relevant literature in the management of spinal subdural abscesses is reviewed.

Neuro-glial hamartoma of the suprasellar cistern.

A unique case of a suprasellar hamartoma in a 29-year-old woman is presented. The lesion was discovered in the context of a work-up for amenorrhea that had lasted 1 year and was resistant to clomiphene and medroxyprogesterone acetate treatment. Magnetic resonance imaging (MRI) revealed a 1.2-cm anterior suprasellar lesion with no apparent connection to the hypothalamus or hypophysis. She underwent surgical resection of the mass. Pathologic examination revealed randomly arranged mature neurons, glial tissue, and myelinated fibers. There was no evidence of gonadotropin-releasing hormone producing neurons on immunohistochemical studies. Postoperative MRI showed complete resection of the lesion, and 1 year later mensus resumed off medication.

Effect of surgical repair on the neurologic function in infants with lipomeningocele.

Eighteen children under the age of 1 year underwent surgery for lipomeningocele at our institution between 1983 and 1991. All the patients had neurologic exams and urodynamic studies (UDS) including a cystometrogram and electromyography of the external urethral sphincter pre- and postoperatively. The surgical procedure performed included an untethering of the spinal cord, laser debulking of the lipoma and placement of a dural graft. All the infants presented with a lesion on their back. Two of 10 infants with a normal neurological exam had abnormal UDS preoperatively. Early surgery normalized abnormal preoperative UDS in 5 of 6 (83%) infants with abnormal UDS. Moreover, 3 of 8 (38%) infants with an abnormal neurological exam preoperatively improved after surgery and none worsened. These observations suggest that abnormal urinary tract function in infants with lipomeningocele may be reversible with early prophylactic surgery.

"Acquired" Chiari I malformation after multiple lumbar punctures: case report.

The authors present the history of a patient with a Chiari I malformation "acquired" after multiple traumatic lumbar punctures. The genesis of tonsillar descent is believed to be related to persistent leakage of cerebrospinal fluid secondary to the multiple traumatic lumbar punctures. The topic of acquired Chiari I malformations and complications of lumbar puncture is reviewed.

Cavernous angioma of the posterior fossa dura mimicking a meningioma: case report and review of literature.

A cavernous angioma of the posterior fossa dura was discovered incidentally on neuroimaging studies. The clinical and pathologic features of this lesion are described. Although it has been reported to arise in the posterior fossa and the tentorium cerebelli, we present the first case of such a malformation arising from the dura of the posterior fossa.

Bladder functional changes resulting from lipomyelomeningocele repair.

From 1986 to 1991, 12 boys and 23 girls underwent surgery for lipomyelomeningocele removal. Of these patients 29 were 15 months old or younger (average age 3 months), while 6 were 4.5 to 19 years old (average age 10 years). Preoperative and postoperative urodynamic studies, including external urethral sphincter electromyography, were done on everyone. All 29 infants had a cutaneous lesion overlying the lower back and 14 had an abnormal neurological examination. Preoperative urodynamic studies were abnormal in 11 patients, consisting of an upper motor neuron lesion in 6, and a mixed upper and lower motor neuron lesion in 5. Postoperatively, 10 of 14 children with an abnormal neurological examination improved, while 9 of 11 with abnormal lower urinary tract function normalized. In 1 of 18 children (6%) with normal preoperative urodynamic studies detrusor-sphincter dyssynergia developed postoperatively. In all 6 older children urinary incontinence developed, and this led to the diagnosis. Everyone had an abnormal neurological examination and abnormal preoperative urodynamic studies. One child had a lower motor neuron lesion, and 5 had a mixed upper and lower motor neuron lesion. Postoperatively, the neurological examination improved in only 1 patient (16%), and the urological symptoms and urodynamic findings improved in another child. Lipomyelomeningocele has a progressive effect on lower spinal cord function because infants tend to present with fewer urinary manifestations and physical findings than older children. Individuals who escape early detection tend to have a more subtle cutaneous abnormality. As a result, older children are more likely to present with urological and neurological complaints. Surgical correction in infancy provides a degree of reversibility not seen in older children. It is imperative that early identification, evaluation and treatment be undertaken to prevent this progression and permanency of neurological changes and urinary dysfunction.

Harvey Cushing's postoperative sketches of pediatric brain tumors.

Harvey Cushing was a man of many talents. Not only was he a premier surgeon and scientist, but a prolific author and artist as well. In this paper, we present two postoperative sketches of pediatric brain tumors drawn by Dr. Cushing. These sketches are representative of drawings which accompany many of his operative notes at the Peter Bent Brigham Hospital. About 25% of Cushing's surgical sketches depict operations performed on children. The most commonly drawn childhood tumors were craniopharyngiomas and gliomas of the brain stem and cerebellum. These drawings reveal how Cushing maintained detailed records of his surgical experience. It is clearly evident from these records that Dr. Cushing gained substantial experience in the treatment of pediatric brain tumors.

Retinal transplants into the anterior chamber of the rat eye.

Developing retinas from 13-18-day fetuses and 2-day neonatal Long-Evans rats transplanted into the anterior chamber of adult eyes of the same or different strain (Lewis) survive and differentiate. Light and electron microscopic studies show that the transplants undergo histogenetic differentiation, resulting in the development of neurons and Müller glial cells and formation of nuclear and plexiform layers. Vascular connections develop between the host iris and the retinal transplant. Vessels and nerves, presumably of iridal origin, were seen on the surface of some transplants. Possible manifestations of graft rejection were monitored; signs of tissue rejection in transplants performed in the Long-Evans rats, an outbred strain, were rare and if present they were mild, at least during the survival periods of up to 91 days allowed in these experiments. Transplants into the eyes of Lewis rats were also well tolerated during the survival period. These observations indicate that retinal transplantation to the adult eye of a genetically different host can be successfully achieved and that both embryonic and perinatal retinas are suitable as donor tissue for ocular transplants. The procedure offers ample opportunities for the study of problems related to retinal plasticity.