Implementation of a spatially multiplexed pixelated three-dimensional display by use of a holographic optical element array

A pixelated holographic stereogram is proposed and experimentally studied for the emulation of a spatially multiplexed composite three-dimensional (3-D) pixel display. With this approach, pixelated holograms are utilized to compose spatially multiplexed images. Each composite pixel in the holographic optical element array has a diffraction pattern that scatters light into predefined spatial directions. Under reconstruction, each pixel generates different intensities along a range of viewing angles. When the composite holographic pixel array is assembled, it has the capability to deliver 3-D effects. The technique, together with a novel recording scheme that is designed to synthesize a computerized 3-D display system based on this concept, is described in some detail.

Periodontics and its influence on aesthetics

The gingival tissues form the soft tissue frame of the dentition and play an important role in dental aesthetics in the maxillary anterior region of the mouth. Alterations to the form and symmetry of the gingivae through developmental, pathologic or iatrogenic factors can significantly alter the appearance and harmony of the natural dentition or prosthetic tooth replacement. This paper describes the techniques available for the management of gingival recession and for surgical lengthening of the clinical crown with particular emphasis on diagnosis and case selection.

Neuropsychological function in patients with nasopharyngeal carcinoma after radiotherapy

A neuropsychological test battery was administered to 27 adult patients with nasopharyngeal carcinoma (NPC) who had received radiotherapy, 28 adult patients with NPC awaiting radiotherapy, and 35 normal adult controls. The 27 patients with radiotherapy had a conventional dosage, 220 cGy per fraction, or less. The median interval between the completion of radiotherapy and the evaluation of neuropsychological function was 1.7 years. Groups were matched for age and educational level. The results showed that our NPC group with radiotherapy had neuropsychological impairments in the areas of auditory attention/concentration, immediate and delayed verbal recall and immediate visual recall, and recent memory, higher-order visuospatial abilities, and bimanual dexterity. Thus neuropsychological dysfunction may occur in patients with NPC within the first 2 years after radiotherapy.

Haemophilus influenzae meningitis in adults

Haemophilus influenzae meningitis is rare in adults. We reviewed the microbiological records of cerebrospinal fluid (CSF) and blood cultures and the medical records of patients with bacterial meningitis admitted to Chang Gung Memorial Hospital from January 1978 to May 1996. Haemophilus influenzae meningitis was found in six adult patients, accounting for 1.8% of 326 bacteriologically proven adult cases of meningitis diagnosed between January 1984 and May 1996. Predisposing conditions included head trauma and/or neurosurgical procedure in four patients and an extracranial extension of a pituitary adenoma in a diabetic patient. None of them had altered consciousness on the day of treatment. A CSF cell count less than 500 x 10(6) leukocytes/liter was noted in three patients. Antibiotic therapy was successful in all patients. Thus, predisposing conditions, particularly head trauma and/or neurosurgical procedure, are commonly present in adult patients with H. influenzae meningitis. Patients with the infection may have a low cellular count in the CSF that may be readily misinterpreted as meningitis caused by other pathogens.

Lhermitte-Duclos disease: first report in Taiwan

We report a case of Lhermitte-Duclos disease (dysplastic gangliocytoma of the cerebellum), an uncommon disorder of uncertain pathogenesis characterized by disarrangement of the normal cerebellar laminar cytoarchitecture. A 40-year-old man was admitted because of vomiting and syncope of a few days' duration, and a 2-month history of intermittent headaches and unsteady gait. A computed tomographic scan of the patient's head showed obstructive hydrocephalus due to displacement of the fourth ventricle by a large, nonenhancing cerebellar mass. The magnetic resonance images of the brain also revealed a space-occupying lesion within the right cerebellum with unusual septation. After surgery, the histologic examination confirmed the diagnosis of Lhermitte-Duclos disease. This is the first report of Lhermitte-Duclos disease in Taiwan.

Expression of nerve growth factor and trkA after transient focal cerebral ischemia in rats

BACKGROUND AND PURPOSE

In vitro studies have shown that nerve growth factor (NGF) is protective to cortical neurons against various insults. However, the role of NGF in relation to its high-affinity trkA receptor in the cortical neurons has not been well discussed. In this experiment, we studied the possible involvement of the NGF/receptor system in the ischemic injury of cortical neurons after focal cerebral ischemia in rats.

METHODS

Male Wistar rats received right middle cerebral artery occlusion of 90 minutes' duration. The rats were decapitated at different reperfusion time points: hour 4 and days 1, 3, 7, and 14 of recirculation. Brain sections at the level of striatum were immunostained against NGF, trkA, glial fibrillary acidic protein (GFAP), and stress protein HSP70. Double immunostaining against NGF and GFAP was also performed. Optical density of NGF immunoreactivity in the ischemic and nonischemic cortexes was compared between sham-control and ischemic animals.

RESULTS

In the sham-control rats, NGF immunoreactivity was present in the cortical and striatal neurons. However, beginning at hour 4 after recirculation, there was a significant decrease of NGF in the ischemic cortex and striatum. Beginning at day 1, NGF was absent completely in the infarcted striatum and cortex. However, in the peri-infarct penumbra area, despite a decrease in NGF at hour 4 and day 1, NGF recovered beginning at day 3 and returned almost to the sham-control level at day 14. In the nonischemic cortex, NGF increased beginning at hour 4, peaked at day 7, and returned almost to the sham-control level at day 14. The trkA and HSP70 immunoreactivities were not present in the sham-control cortex. However, trkA was induced at hour 4 in the ischemic cortex and at days 1 and 3 in the peri-infarct penumbra cortex. The HSP70 was induced at days 1 and 3 in the peri-infarct penumbra area. Double immunostaining showed that the number of GFAP-positive cells increased gradually, and NGF immunoreactivity in the GFAP-positive cells became gradually intense after ischemia.

CONCLUSIONS

Our study demonstrated a temporal profile of NGF and trkA in the ischemic cortex and NGF expression by reactive astrocytes. Our data suggest that the NGF/receptor system may play a role in the astrocyte/neuron interaction under certain pathological conditions, such as focal cerebral ischemia.

In vitro cell-free conversion of noninfectious Moloney retrovirus particles to an infectious form by the addition of the vesicular stomatitis virus surrogate envelope G protein

In the absence of envelope gene expression, retrovirus packaging cell lines expressing Moloney murine leukemia virus (MLV) gag and pol genes produce large amounts of noninfectious virus-like particles that contain reverse transcriptase, processed Gag protein, and viral RNA (gag-pol RNA particles). We demonstrate that these particles can be made infectious in an in vitro, cell-free system by the addition of a surrogate envelope protein, the G spike glycoprotein of vesicular stomatitis virus (VSV-G). The appearance of infectivity is accompanied by physical association of the G protein with the immature, noninfectious virus particles. Similarly, exposure in vitro of wild-type VSV-G to a fusion-defective pseudotyped virus containing a mutant VSV-G markedly increases the infectivity of the virus to titers similar to those of conventional VSV-G pseudotyped viruses. Furthermore, similar treatment of an amphotropic murine leukemia virus significantly allows infection of BHK cells not otherwise susceptible to infection with native amphotropic virus. The partially cell-free virus maturation system reported here should be useful for studies aimed at the preparation of tissue-targeted retrovirus vectors and will also aid in studies of nucleocapsid-envelope interactions during budding and of virus assembly and virus-receptor interactions during virus uptake into infected cells. It may also represent a potentially useful step toward the eventual development of a completely cell-free retrovirus assembly system.

Bipolar disorder in late life: a review

Although there is a broad base of literature on depression among elderly patients and on mania in younger patients, there is a relative paucity of information on bipolar disorder in the elderly population. While the quantities of data reflect the relative prevalences of these illnesses, there is evidence to suggest that classification of mania in the elderly with respect to age of onset, natural course, family history, and pathophysiology may be useful in understanding the heterogeneous etiologies of this syndrome. This paper presents a review of the literature on the incidence and course of illness in late-life bipolar disorder. Further, dilemmas of diagnostic classification in relation to associated risk factors will be discussed.

Chemical mechanism of the endogenous argininosuccinate lyase activity of duck lens delta2-crystallin

The endogenous argininosuccinate lyase activity of duck delta2-crystallin was specifically inactivated by the histidine-specific reagent, diethyl pyrocarbonate. The protein was protected by l-citrulline or l-arginine from the diethyl pyrocarbonate inactivation. To characterize further the chemical mechanism of the delta2-crystallin-catalysed reaction, deuterium-labelled argininosuccinate was enzymically synthesized from fumarate and l-arginine with delta2-crystallin in 2H2O. The argininosuccinate synthesized contained about 19% of the anhydride form; however, the deuterium was clearly demonstrated to be incorporated enantioselectively. Only the pro-HR atom at C-9 of the succinate moiety was labelled in the [2H]argininosuccinate-9-d synthesized, which indicates an anti-elimination mechanism for the endogenous argininosuccinate lyase activity of delta2-crystallin. The enzymic activity of duck lens delta2-crystallin in the pH range 5.5-8.5 was investigated using both protium- and deuterium-labelled argininosuccinate as the substrate. From the logkcat versus pH plot, two molecular pKa values of 6.18+/-0.02 and 8.75+/-0.03 were detected in the delta2-crystallin-argininosuccinate binary complex. The former must be dehydronated and the latter hydronated to achieve an optimum reaction rate. The logkcat/Km versus pH plot suggested two molecular pKa values of 5.96+/-0.09 and 8.29+/-0.10 for the free delta2-crystallin to be involved in the substrate binding. Small kinetic isotope effects of 1.17+/-0.02 and 1.05+/-0.09 were found for kcat and kcat/Km respectively. Combining results from labelling and kinetic analysis indicates that the endogenous argininosuccinate lyase activity of duck delta2-crystallin is compatible with a stepwise E1cB mechanism, the rate-limiting step probably at the C-N bond-cleavage step.

Hypoplasia of the internal carotid artery with intercavernous anastomosis

We report a symptomatic case of unilateral hypoplasia of the internal carotid artery with an intercavernous anastomosis, a very rare developmental anomaly. The symptoms were caused by occlusion of the proximal middle cerebral artery which possibly related to the haemodynamic stress caused by the anomalous intercavernous anastomosis.

Extent of collateral sprouting of intact nerve fibers in rats depends on the local availability of nerve growth factor

We investigated the influence of local administration of anti-nerve growth factor (NGF) serum on collateral nerve fiber sprouting caused by chronic constriction injury (CCI) of the sciatic nerve in rats. CCI was induced in adult Sprague-Dawley rats (six per group) by constriction of the sciatic nerve of the right hind limb. Control rats received no further manipulation. In four other groups, rabbit preimmune (control) serum or low (18 ng) or high (1800 ng) doses of anti-NGF serum were injected into the operated or unoperated hind limb each day for 1 month. We used an Evans dye-labeled plasma extravasation technique to visualize the extent of collateral sprouting. Local injection of anti-NGF serum at both high and low doses, but not control serum, significantly reduced the spread of collateral sprouting from the saphenous nerve into the sciatic nerve innervation territory. High-dose anti-NGF serum did not block collateral sprouting when injected into the contralateral (unoperated) hind limb, indicating that the inhibition of sprouting was not caused by a systemic effect. In conclusion, local administration of anti-NGF serum can block sprouting of collateral fibers after nerve injury. Our findings suggest that collateral sprouting is dependent on the local availability of NGF to nearby intact cutaneous nerve fibers.

The overexpression of Bax produces cell death upon induction of the mitochondrial permeability transition

Stably transfected Jurkat T cells were produced in which Bax expression is inducible by muristerone A. The cell death resulting from induction of the overexpression of Bax was prevented by inhibition of the mitochondrial permeability transition (MPT) with cyclosporin A (CyA) in combination with the phospholipase A2 inhibitor aristolochic acid (ArA). The caspase-3 inhibitor Z-Asp-Glu-Val aspartic acid fluoromethylketone (Z-DEVD-FMK) had no effect on the loss of viability. The MPT was measured as the CyA plus ArA-preventable loss of the mitochondrial membrane potential (DeltaPsim). The MPT was accompanied by the release of cytochrome c from the mitochondria, caspase-3 activation in the cytosol, cleavage of the nuclear enzyme poly(ADP-ribose)polymerase (PARP), and DNA fragmentation, all of which were inhibited by CyA plus ArA. Z-DEVD-FMK had no effect on the loss of DeltaPsim and the redistribution of cytochrome c but did prevent caspase-3 activation, PARP cleavage, and DNA fragmentation. It is concluded that Bax induces the MPT, a critical event in the loss of cell viability. In addition to the cell death, the MPT mediates other typical manifestations of apoptosis in this model, namely release of cytochrome c, caspase activation with PARP cleavage, and DNA fragmentation.

Growth status in children with cystic fibrosis based on the National Cystic Fibrosis Patient Registry data: evaluation of various criteria used to identify malnutrition

OBJECTIVES

The objectives of this study were to determine growth status and to identify malnutrition with various anthropometric indicators in children with cystic fibrosis (CF) based on cross-sectional analysis of the 1993 National CF Patient Registry data.

METHODS

Heights and weights of 13,116 children with CF were evaluated with percentile, percent of reference median, Z-score, and percent ideal weight-for-height based on National Center for Health Statistics/Centers for Disease Control growth references. Malnutrition was defined by four criteria: (1) height-for-age <5th percentile ("stunting") or weight-for-age <5th percentile ("wasting") (2) height-for-age <90% of reference median or weight-for-age <80% of reference median, (3) height-for-age <5th percentile or percent ideal weight-for-height <85%, and (4) height-for-age <90% of reference median or weight-for-height <85% of reference median.

RESULTS

Mean and median height- and weight-for-age were found to be at the 30th and 20th percentiles in children with CF. Malnutrition (height- or weight-for-age <5th percentile) was particularly pronounced in infants (47%) and adolescents (34%) and patients with newly diagnosed CF (44%). A significant sex difference (p < 0.01) in the occurrence of stunting (height-for-age <5th percentile) was observed during adolescence: boys 11 to 14 years of age showed lower occurrence of stunting (19%) compared with girls (29%), whereas the opposite trend was observed at 15 to 18 years (34% in male patients vs 28% in female patients).

CONCLUSION

Twenty percent of all children in the 1993 National CF Patient Registry were <5th percentile for height- or weight-for-age. A significant discrepancy was found when different criteria were used to distinguish "stunting" versus "wasting" in malnourished children with CF.

Hirayama disease: MR diagnosis

We report the MR findings in two cases of Hirayama disease, a kind of cervical myelopathy related to flexion movements of the neck. In flexion MR studies, we can see the striking and pathognomonic picture of anterior shifting of posterior dura at the lower cervical spinal canal. In nonflexion studies, we find that asymmetric cord atrophy, especially at the lower cervical cord, though subtle, is highly suggestive of Hirayama disease. When it is seen, a flexion MR study is warranted to prove this diagnosis.

Genomic organization and characterization of the promoter region of the round-spotted pufferfish (Tetraodon fluviatilis) JAK1 kinase gene

Seventeen kilobases of genomic DNA containing the promoter and the coding region of the round-spotted pufferfish JAK1 gene was isolated and completely sequenced. This gene consists of 25 exons and 24 introns spanning about 13.5 kb, compared to > 30kb in carp JAK1 gene. Primer extension analysis revealed one transcription initiation site which was 376 bp upstream of the translation initiation site. The sequence of the 2.9 kb region upstream of the transcription initiation site contains numerous potential binding sites for transcription factors including HNF-5, GCF, Sp1, CRE, AP2, GATA, GAGA, E2A, p53, and NF-IL6. When this region was placed upstream of the chloramphenicol acetyltransferase (CAT) reporter gene and transfected into a carp CF cell line, it could drive the synthesis of CAT enzyme three times more efficiently than could the common carp JAK1 promoter.

Factors that affect the expression of beta-amyloid precursor protein immunoreactivity in the rat retina

Expression of beta-amyloid precursor protein immunoreactivity in the rat retina was studied after intravitreal injection of substances known to influence neural function in different ways. The substances were the excitatory amino acid glutamate, the inflammatory agent lipopolysaccharide, the depolarizing agent potassium chloride, and the potassium channel blocker barium chloride. In comparison with controls, more beta-amyloid precursor protein immunoreactivity was observed in the radial process of Müller glial cells 24 hours after injection of glutamate or lipopolysaccharide. In contrast, administration of barium chloride greatly reduced immunostaining in Müller cells. Further, an increase in immunostaining was observed in the inner and outer plexiform layers in retinas treated with any of the 3 chemicals, and in blood vessels after injection of glutamate and lipopolysaccharide. These observations suggest that multiple but specific signaling pathways are involved in regulating expression of beta-amyloid precursor protein in distinct cell types and regions in the retina.

Dominant negative activity of mutant thyroid hormone alpha1 receptors from patients with hepatocellular carcinoma

Complementary DNAs for two mutant thyroid hormone alpha1 receptors (TR alpha1) were isolated from hepatocellular carcinomas of two patients. Sequence analyses of the complementary DNAs showed a single Val390Ala and double Pro398Ser/Glu350Lys mutations in mutants H and L, respectively. We characterized their hormone-binding, DNA-binding, and dominant negative activities. Mutants H and L did not bind the hormone T3. Their DNA-binding activities were analyzed using three types of thyroid hormone response elements (TREs) in which the half-site binding motifs are arranged in an everted repeat (Lys), an inverted repeat (Pal), or a direct repeat separated by four nucleotides (DR4). Compared with wild-type TR alpha1 (w-TR alpha1), which bound these TREs with different homodimer/monomer ratios, binding of mutant L to the three TREs as homodimers was reduced by approximately 90%. However, binding of mutant H to these TREs was more complex. Although it bound normally to DR4 as homodimers, its binding to Lys as homodimers was reduced by approximately 80%. Surprisingly, its binding to Pal was markedly enhanced compared with w-TR alpha1. The binding of these two mutants to the three TREs as heterodimers with retinoid X receptors (RXR alpha and -beta) was not significantly affected. Consistent with the lack of T3-binding activity, both mutants had lost their trans-activation capacity. Mutants H and L exhibited dominant negative activity, but differed in their TRE dependency. The dominant negative potency of mutant H was in the rank order of Pal > DR4 > Lys, whereas no TRE dependency was observed for mutant L. The present study indicates that mutations of the TR alpha gene do occur in patients and that these novel TR alpha1 mutants provide a valuable tool to further understand the molecular basis of the dominant negative action of mutant TRs.

Myasthenia gravis and Charcot-Marie-Tooth disease type 1A: an unusual combination of diseases

Concurrence of myasthenia gravis (MG) and Charcot-Marie-Tooth type 1 (CMT1A) neuropathy is rare. We describe a 60-year-old woman with MG and genetically proved CMT1A. The fluctuating ocular symptoms and proximal limb weakness were markedly improved by pyridostigmine treatment. Recognition of the possible association of MG and CMT1A in the same patient is important because the therapeutic result is rewarding.

Kinetic studies of the inhibitory effects of propeptides subtilisin BPN' and Carlsberg to bacterial serine proteases

The propeptides of bacterial subtilisin BPN' and Carlsberg were synthesized to investigate their inhibitory function on the enzymes. Kinetically, pro-BPN' inhibits the proteolytic activities of subtilisin BPN' and Carlsberg separately in a slow binding mode. Pro-Carlsberg behaves as a typical rapid equilibrium competitive inhibitor for these two proteases. Functionally, pro-Carlsberg inhibits the subtilisins with moderate selectivity. The inhibition constant Ki of pro-BPN' to subtilisin BPN' is 5.0 nM, and 6.1 nM to subtilisin Carlsberg. The on-rate of pro-BPN' to subtilisin BPN' is 5.8 x 10(5) M(-1)s(-1), and the off-rate 2.9 x 10(-3) s(-1). Similarly, the on-rate of pro-BPN' to subtilisin Carlsberg is 2.2 x 10(5) M(-1)s(-1), and the off-rate 1.3 x 10(-3) s(-1). On the other hand, the Ki of pro-Carlsberg to subtilisin BPN' gives 1.3 x 10(2) nM, and 88 nM to subtilisin Carlsberg. Based on the key features of the interactions between pro-BPN' and subtilisin from X-ray crystallographic results (Gallagher et al., 1995), the correlation between the sequence of subtilisin propeptides and their inhibition abilities on the proteases are compared and discussed.

Klebsiella meningitis in Taiwan: an overview

Klebsiella infection has been considered to be an uncommon cause of meningitis. To determine its incidence and clinical features, we reviewed the microbiologic records of cerebrospinal fluid (CSF) and blood cultures and the medical records of patients with bacterial meningitis admitted between 1981 and 1995. Klebsiella meningitis was diagnosed in 79 patients with 83 episodes. All patients had klebsiella isolated from CSF and/or blood and typical symptoms and signs of acute bacterial meningitis. Of these, 74 were over 16 years of age and 2 of the 5 children were infants. There was an increased prevalence rate of klebsiella meningitis after 1986. Of the 83 episodes, only 9 occurred between 1981 and 1986, accounting for 7.8% of 115 cases with CSF and/or blood culture-proven acute bacterial meningitis, whereas in 1987-95, there were 74 episodes accounting for 17.7% of 419 bacteriologically proven cases. K. pneumoniae accounted for 69 episodes, K. oxytoca, 11 episodes and K. ozaenae, 3 episodes. Male gender, diabetes mellitus and liver cirrhosis were commonly associated with K. pneumoniae meningitis. Neurosurgical procedures were frequently associated with K. oxytoca meningitis. All three patients with K. ozaenae meningitis had a primary disease of the nasopharyngeal pathway. The mortality rate due to K. pneumoniae was 48.5%, K. oxytoca, 10% and K. ozaenae, 0%. In patients with K. pneumoniae meningitis, poor prognostic factors included age over 60 years, diabetes mellitus, bacteremia and severe neurological deficits on the first day of treatment.

Guillain-Barré syndrome in Taiwan: a clinical study of 167 patients

OBJECTIVE

To identify clinical characteristics of various forms of Guillain-Barré syndrome in Taiwan.

METHODS

The clinical and electrophysiological data of 167 consecutive patients with Guillain-Barré syndrome admitted to Chang Gung Memorial Hospital, a general paediatric and adult hospital in Taiwan, were reviewed.

RESULTS

Analysis of age distribution disclosed a high incidence (21%) among patients under the age of 10 years. Seasonal preponderance in Spring (March to May) was found. Utilizing clinical and electrophysiological data, these 167 patients with Guillain-Barré syndrome were subclassified; 82 (49%) had acute inflammatory demyelinating polyradiculoneuropathy (AIDP), 32 (19%) had Fisher syndrome (FS), and six (4%) had axonal forms of Guillain-Barré syndrome. The remaining 47 (28%) patients were unclassified. Patients with AIDP and FS had many common clinical features, including seasonal distribution, history of preceding illness, sensory abnormalities, cranial nerve involvement except for extraocular motor nerves, and albuminocytological dissociation on examination of CSF. Follow up study on 145 patients disclosed that 127 (87%) recovered satisfactorily, 14 (10%) were persistently disabled, and four (3%) died during admission to hospital. Clinical features associated with poor outcome (persistent disability or death) were requirement for mechanical ventilation, a low mean compound muscle action potential amplitude (< or = 10% of the lower limit of normal), and age greater than 40 years.

CONCLUSION

Guillain-Barré syndrome in Taiwan showed a peculiar age and seasonal distribution and a high frequency of FS not seen in other series. Given that patients with AIDP and FS had many common clinical features, AIDP and FS may have similar underlying pathological mechanisms.

Dual-input hybrid acousto-optic set-reset flip-flop and its nonlinear dynamics

The characteristics of a dual-input hybrid acousto-optic device are investigated numerically and experimentally. The device, which operates as a set-reset flip-flop, uses the well-known bistable acousto-optic device with feedback to which two input beams are applied. The resulting flip-flop is analyzed numerically by use of nonlinear dynamical and nonlinear circuit-modeling techniques, and some of its properties are demonstrated experimentally.

NMR and circular dichroism studies on the conformation of a 44-mer peptide from a CD4-binding domain of human immunodeficiency virus envelope glycoprotein

Two-dimensional NMR, circular dichroism (CD) experiments and molecular modeling were performed to study the secondary structure of a 44-mer peptide fragment derived from the C4 region of gp120 of human immunodeficiency virus in aqueous solution. It was found a nascent helical structure exists following a type I turn near the N-terminus of the peptide. The proline residue in the turn appears to serve as a helix initiator. The helical structure was in fast dynamic equilibrium with beta- or random coil form on the NMR scale. A reverse turn was identified at a section containing two consecutive proline residues. A nascent helical structure has been detected for the region near the C-terminus of the 44-mer peptide. Higher helical content for the peptide is also indicated by CD studies on TFE titration. Thus it is proposed that, in more apolar medium, the Pro-Pro turn and the segment amino-terminal to it, spanning about 20 amino acids, may be converted into helix structure. Moreover, the region near the C-terminus of the peptide may also be induced into helix, so that a helix-turn-helix structure may be formed in the C4 domain of gp120. A helical wheel representation of this stretch shows amphipathicity of the helix. The biological implication of the conformational adaptibility of the peptide was discussed.

Extracranial distal aneurysm of posterior inferior cerebellar artery

An unusual aneurysm arising from an extracranial lateral medullary segment of the posterior inferior cerebellar artery (PICA) is reported. The origin of the PICA was also extracranial, 10 mm below the foramen magnum. The aneurysm was not seen on three-vessel angiography. The literature is reviewed with regard to the clinical and radiological features of such aneurysms. Occipital and nuchal headache with an altered level of consciousness, intraventricular haemorrhage, and hydrocephalus are suggestive of such aneurysm. The need for four-vessel angiography is again stressed.

The role of the N-terminal leucine residue in snake venom cardiotoxin II (Naja naja atra)

The N-terminal leucine residue of snake venom cardiotoxin II (CTX II) (Naja naja atra) was systematically replaced with D-leucine (CTXII-L1-D-L), glycine (CTXII-L1G) or deleted [CTXII-(2-60)] to study the role of leucine residue in CTX II molecule. CTX II, CTXL1-D-L, CTXL1G and CTX(2-60) were produced by chemical synthesis method and purified by high performance liquid chromatography. Owing to folding problem in CTXII-(2-60), only CTX II, CTXII-L1-D-L and CTXII-L1G were produced in a pure form and characterized by amino acid analysis, mass spectrometry and peptide mapping. In the structural aspect, changing the Leu-1 by D-Leu or Gly causes a drastic alteration in the whole CTX II structure as detected by circular dichroism, 1-anilino-naphthalene-8-sulfonate (ANS) fluorescence assay. In the functional aspect, both CTXII-L1-D-L and CTXII-L1G are still retained substantial biological activity of CTX II. Therefore, the results indicate that both the chirality and the side-chain of the N-terminal leucine residue of CTX II are important elements in maintaining the whole CTX II structure. In addition, this study is the first report in elucidating the reason why the first N-terminal residue of most CTXs (90.3%) is leucine residue.