Case report: unilateral haematocolpos in uterine duplication associated with renal agenesis

A case of unilateral haematocolpos correctly diagnosed by ultrasound is described in a 13 year old girl known to have a solitary kidney. The association of renal agenesis with Müllerian abnormalities is well recognised and in this case the ultrasound findings ensured that the correct surgical management was undertaken.     

Mandibular lingual releasing approach.

The mandibular lingual releasing approach to oral cavity and oropharyngeal tumors provides excellent visualization for resection while integrity of the mandibular arch is preserved. A lingual floor-of-mouth flap is created, which allows delivery of these structures directly into the neck without lip splitting, mandibulotomy, or mandibulectomy. The procedure was carried out on 15 patients between 1987 and 1991, with followup ranging from 2 to 50 months. Nine patients had received previous radiation, whereas planned postoperative radiation was administered to five patients. The visualization afforded by this technique was very good, in that 12 patients had clear margins of resection. Three patients had close margins; recurrent disease developed in one of these patients 18 months later. Twelve of the patients were able to maintain their weight with an oral diet alone. Four postoperative fistulae occurred, three of these were in patients who had not been previously irradiated. The single fistula that did not spontaneously heal occurred in a patient who had received previous radiation and was also on long-term corticosteroids. Mandibular osteoradionecrosis developed in two patients who received postoperative radiation. The complication rate after previous radiation is acceptable; however, there is risk of mandibular osteoradionecrosis after high-dose postoperative radiation.     

Ultra-early evaluation of regional cerebral blood flow in severely head-injured patients using xenon-enhanced computerized tomography.

The role of cerebral ischemia in the pathophysiology of traumatic brain injury is unclear. Cerebral blood flow (CBF) measurements with 133Xe have thus far revealed ischemia in a substantial number of patients only when performed between 4 and 12 hours postinjury. But these studies cannot be performed sooner after injury, they cannot be done in patients with intracranial hematomas still in place, and they cannot detect focal ischemia. Therefore, the authors performed CBF measurements in 35 comatose head-injured patients using stable xenon-enhanced computerized tomography (CT), simultaneously with the initial CT scan (at a mean (+/- standard error of the mean) interval of 3.1 +/- 2.1 hours after injury). Seven patients with diffuse cerebral swelling had significantly lower flows in all brain regions measured as compared to patients without swelling or with focal contusions; in four of the seven, cerebral ischemia (CBF less than or equal to 18 ml/100 gm.min-1) was present. Acute intracranial hematomas were associated with decreased CBF and regional ischemia in the ipsilateral hemisphere, but did not disproportionately impair brain-stem blood flow. Overall, global or regional ischemia was found in 11 patients (31.4%). There was no correlation between the presence of hypoxia or hypertension before resuscitation and the occurrence of ischemia, neither could ischemia be attributed to low pCO2. Ischemia was significantly associated with early mortality (p less than 0.02), whereas normal or high CBF values were not predictive of favorable short-term outcome. These data support the hypothesis that ischemia is an important secondary injury mechanism after traumatic brain injury, and that trauma may share pathophysiological mechanisms with stroke in a large number of cases; this may have important implications for the use of hyperventilation and antihypertensive drugs in the acute management of severely head-injured patients, and may lead to testing of drugs that are effective or have shown promise in the treatment of ischemic stroke.     

Learning movement sequences with a delayed reward signal in a hierarchical model of motor function.

A key problem in reinforcement learning is how an animal is able to learn a sequence of movements when the reward signal only occurs at the end of the sequence. We describe how a hierarchical dynamical model of motor function is able to solve the problem of delayed reward in learning movement sequences using associative (Hebbian) learning. At the lowest level, the motor system encodes simple movements or primitives, while at higher levels the system encodes sequences of primitives. During training, the network is able to learn a high level motor program composed of a specific temporal sequence of motor primitives. The network is able to achieve this despite the fact that the reward signal, which indicates whether or not the desired motor program has been performed correctly, is received only at the end of each trial during learning. Use of a continuous attractor network in the architecture enables the network to generate the motor outputs required to produce the continuous movements necessary to implement the motor sequence.     

In the hippocampus in vivo,nitric oxide does not appear to function as an endogenous antiepileptic agent

Using a reverberatory epilepiform discharge of hippocampal-parahippocampal circuits termed maximal dentate activation, this study investigated whether the local release of nitric oxide within these circuits functions as an antiepileptic agent. Two nitric oxide synthase inhibitors (l-nitro-arginine methyl ester and 7-nitro-indazole) and a guanylate cyclase inhibitor (methylene blue) were tested, and none had a significant effect on the time to onset or duration of maximal dentate activation. A membrane-permeable analogue of cyclic guanosine monophosphate (cGMP), 8-bromo-cGMP, caused an increase in the time to onset and a decrease in the duration of maximal dentate activation. The number of neurons expressing NADPH diaphorase activity (a marker for nitric oxide synthase) was also examined after repeated elicitation of maximal dentate activation. After 18 seizures there was a significant, but transient, decrease in the number of hilar/subgranular neurons that were NADPH diaphorase-positive. The decrease was only seen at 1 h after the last seizure. There was no induction of NADPH diaphorase activity. These results are not consistent with the hypothesis that, in hippocampal-parahippocampal circuits in vivo, nitric oxide is released in response to neuronal activity and then acts to terminate the neuronal activity.     

Relative carriage rates of nuclear dehydrogenating clostridia in two populations of different colorectal cancer risk

Carriage of nuclear dehydrogenating clostridia has been associated with colon cancer and implicated in its aetiology. This study has compared the carriage of these organisms in a British population at high risk for the development of colon cancer with a low risk Nigerian population. Clostridia were found in all of the stools from both populations. Nuclear dehydrogenating clostridia were only found in the stools of the British subjects (32%). These results support the suggestion that the carriage rate of nuclear dehydrogenating clostridia in a population is related to the risk of colon cancer.