W.H. Kwong

Postnatal Developmental Changes of Vitreous and Lens Volumes in Sprague-Dawley Rats

Purpose: To study the postnatal changes in the vitreous and lens volumes in Sprague-Dawley rats. Methods: Six eyes from Sprague-Dawley rats at each age (postnatal days 1, 6, 12, 21, 30 and 120) were obtained and cryosectioned without fixation. The areas of vitreous, lens and intraocular cavity in the sections were measured separately and their volumes calculated. The percentages of vitreous and lens volumes in the intraocular cavity of each eye were also calculated. Results: The rat vitreous volumes (means ± SE) were 5.2 ± 0.5 µl on day 1, 13.4 ± 0.6 µl on day 6, 22.2 ± 1.0 µl on day 12, 27.8 ± 0.6 µl on day 21, 33.3 ± 1.3 µl on day 30 and 52.4 ± 1.9 µl on day 120. The lens volumes were 3.5 ± 0.2 µl, 7.7 ± 0.4 µl, 10.6 ± 0.4 µl, 15.1 ± 0.5 µl, 19.6 ± 0.8 µl and 43.0 ± 1.3 µl, respectively, in each time group. The vitreous and lens measurements revealed different growth rates and trends. Conclusion: Our systematic data quantify the postnatal development of the lens and the vitreous, and also provide a reference for the ocular volumes of rats at specific postnatal ages.

Myelination of the pig's brain: a correlated MRI and histological study.

Minipigs, 2, 4, 6 months old, were used to evaluate the relationship between myelination in the fiber tracts of the central nervous system (CNS) of this animal during development. Histological results showed an increased density of the myelinated fibers as well as branching of these fibers in the areas studied, including the cortical white matter, olfactory tract, the corticospinal tract, the fasciculus cuneatus and the spinal V nucleus from 2 to 6 months old. By 6 months, the pig was sexually matured. Concomitantly, there was an increase in high signal-intensity regions (sites) in the magnetic resonance T1-weighted images as myelination progressed. There is a good correlation between the histologically observed progress of myelination and the T1-weighted images in the development of the CNS of the pig.

Profiles of serotonin receptors in the developing human thalamus

The critical importance of the thalamus and its serotonergic innervation with respect to neuropsychiatric syndromes is increasingly recognized. This study investigates the localization of serotonin (5-hydroxytryptamine; 5-HT) receptors by immunohistochemistry in the thalamic nuclei of human fetuses aged 21 to 32 weeks of gestation. Results indicate that, already at 21 weeks of gestation, two 5-HT receptors are present in the dorsomedial nucleus of the developing thalamus: 5-HT2A receptors are localized in neurons and 5-HT2C receptors in fibers. By 31 and 32 weeks of gestation, 5-HT1A and 5-HT4 receptors are also detected in neuronal fibers of the same nucleus. At this later developmental stage, the percentage of 5-HT2A labeled neurons has significantly increased in the dorsomedial nucleus, and 5-HT2C positive neurons are observed in the centromedian and lateroventral thalamic nuclei as well. In contrast, neither neuronal cells nor fibers display any immunoreactivity for 5-HT3 or 5-HT6 receptors at any of the ages examined. Our observation that 5-HT1A, 5-HT2A, 5-HT2C and 5-HT4 receptors are present in the human thalamus prenatally indicates that 5-HT may play a role during fetal development. Disrupted development of the thalamic serotonergic system during this gestational period may contribute to the pathophysiology of neuropsychiatric disorders.

Premedication with Intravenous Ketorolac Trometamol (Toradol ® ) in Colonoscopy: A Randomized Controlled Trial

OBJECTIVE:We conducted a prospective double-blinded placebo-controlled randomized trial to investigate the effect of ketorolac trometamol (KT) administered intravenously as premedication in colonoscopy.METHODS:One hundred and forty patients undergoing colonoscopy were randomized to receive either 60 mg of KT (KT group (KTG), n = 70) or placebo (normal saline group (NSG), n = 70) intravenously as premedication 30 min prior to procedure. Patient-controlled sedation (PCS) was used as the mode of sedation. Outcome measures included patient self-assessed pain score in a 10-cm unscaled visual analog scale (VAS), endoscopist assessment of patient pain score in VAS, patients willingness to repeat colonoscopy, administered and demanded doses of PCS, patient satisfaction score in VAS, and hemodynamic changes during and after the procedure.RESULTS:The mean patient self-assessed pain score (SD) during procedure was significantly lower in KTG than NSG: 5.08 (2.74) vs 6.62 (2.45); p = 0.001. The mean endoscopist assessment of patient pain score (SD) was significantly lower in KTG than NSG as well: 3.99 (2.80) vs 5.28 (2.71); p = 0.006. More patients in KTG were willing to repeat procedure as compared with NSG (80.0% vs 57.1%; p = 0.004). No significant difference was found in the administered and demanded doses of PCS, mean satisfactory scores and hemodynamic changes in both groups. No serious complication related to intravenous (IV) KT was noted.CONCLUSIONS:Premedication with IV KT (Toradol®) improves pain control during colonoscopy with no associated serious complications.

Different in vitro toxicity of ribosome-inactivating proteins (RIPs) on sensory neurons and Schwann cells.

OBJECTIVE To study the neurotoxicity induced by Ricinus communis agglutinin (RCA), ricin A chain (RTA), and trichosanthin (TCS) in vitro. METHODS Rat neurons and Schwann cells were cultured and real-time up-take of RIPs was traced. TUNEL, Annexin V and DAPI were employed to study the mechanism. RESULTS The purity of both primary neuronal and Schwann cell cultures attained 80-90%. In neuritis, transport of FITC-RCA was demonstrated, but RTA and TCS were not detected. RCA elicited the strongest TUNEL and annexin V signals in both cultures. RTA evoked a stronger apoptotic signal than TCS in neurons. In contrast, compared with TCS, RTA elicited an attenuated apoptotic reaction in Schwann cells. All internalized RIPs were concentrated in the cytoplasm of the cells and their nuclei were not stained by DAPI. CONCLUSION The toxicity of these RIPs on neurons is different from that on Schwann cells. Although they enter cells by different mechanisms they all induce apoptosis. These results may find application in in vivo neural lesioning studies and clinical therapy.

Retrograde transport of a traditional Chinese medicine, α-trichosanthin, and its selective neural toxicity

Objective. To investigate the peripheral neuronal toxicity of a traditional Chinese medicine, α-trichosanthin (TCS). Methods. TCS and rhodamine-conjugated TCS were separately injected into the rat sciatic nerve. Saline and rhodamine were used alone and separately as control solutions. The motor neurons in the spinal cord and sensory neurons in the dorsal root ganglia were separately counted. The entry of TCS molecules into neurons was observed under the fluorescence microscope. The glial reactions were studied by lectin staining and immunohistochemical method. The muscles innervated by the sciatic nerve and distal to the injection sites, and the nerves proximal to the injection sites were also collected and examined. Results. TCS was taken up and transported by peripheral axons, and at a dose of 1 nmol, killed more than 90% of the motor neurons in 5 days, but only one-third of the sensory neurons of the injected nerve. The loss of neurons was permanent, while the increase of glial activities was mild and transient. Conclusion. TCS is retrogradely transported by axons of the injected nerve. TCS shows a selective neurotoxicity on different types of neurons. Hence TCS is useful in producing neural lesion in research, and this use may also be of applicational value in treating chronic spasticity, hyperalgesia, and pain.

Three-dimensional reconstruction of brain surface anatomy based on magnetic resonance imaging diffusion-weighted imaging: a new approach.

Fifty normal noninfarct patients and 12 cases with infarcts of the cerebrum were examined with routine magnetic resonance imaging and echo-planar diffusion-weighted imaging. The diffusion-weighted three-dimensional images were reconstructed with volume-rendering processing on workstation. Precentral gyrus, postcentral gyrus, superior parietal lobule, superior frontal gyrus, precentral sulcus, central sulcus, postcentral sulcus, intraparietal sulcus and superior frontal sulcus were best shown of all structures with an arbitrary score of 2.61-2.77. Supramarginal gyrus, middle frontal gyrus, inferior frontal gyrus and lateral sulcus were clearly shown in the majority of the cerebra with average scores of 2.0-2.49; angular gyrus, inferior frontal sulcus and superior temporal gyrus were not demonstrated satisfactorily and their average scores were 1.67-1.89. Middle temporal gyrus, inferior temporal gyrus, superior temporal sulcus and inferior temporal sulcus were difficult to identify, and thus had average scores of 0.87-1.26. Brain surface structures were better displayed in the older group of individuals than in the younger group. The structures in the 12 cases with acute or chronic cerebrum infarcts were also satisfactorily demonstrated with this new technique.

Mechanism of the Specific Neuronal Toxicity of a Type I Ribosome-Inactivating Protein, Trichosanthin

The aim was to study the mechanism of neuronal toxicity, the cellular pathway, and the glial cell reactions induced by trichosanthin (TCS), a type I ribosome-inactivating protein (RIP). Ricin A chain (RTA) was included for comparison. TCS, RTA, and fluorescein isothiocyanate (FITC)-labeled TCS and RTA were separately injected into rat eyes. Saline or pure FITC was used as the control. Electron microscopy, confocal microscopy, and lectin and immunohistochemical staining were used to study the neurotoxic mechanism. TCS mainly induced apoptosis by causing degeneration of the mitochondria. TCS was able to enter the Müller and pigment cells. It caused a change in cell number of the following types of glial cells: a decrease in Müller cells, an increase in astrocytes, and little change in microglia. In contrast, RTA mainly induced necrosis and entered vascular endothelial cells. Astrocyte and microglia reactions were stronger in the RTA-treated retinas than those in the TCS-treated retinas. In conclusion, TCS appears to selectively enter and destroy Müller and pigment epithelia cells, which subsequently induce the death of photoreceptors. Degeneration of mitochondria is involved in the pathways of apoptosis of the photoreceptors caused by TCS. In sharp contrast, RTA can enter vascular endothelial cells and damage the vascular endothelium, resulting in retinitis and necrosis.

Retinal twin cones or retinal double cones in fish : Misnomer or different morphological forms?

Scanning retinal electronmicroscopy studies demonstrated the presence of both twin cones (two identical cones adhered together) and double cones (two non-identical cones adhered together) in the retinae of the major forms of fish, which included actinopterygi, elasmobranch, and teleosts. The complexity of these visual cells in the retinae of different groups of fishes was revealed for the first time and reflected on the diversities of functions of the fish retina in general.

Substance P and enkephalin containing fibers in the developing nucleus dorsalis of the human spinal cord

A peroxidase-antiperoxidase immunostaining method was employed to determine the initial stage of appearance and localization of substance P (SP) and enkephalin (ENK) in the nucleus dorsalis of the developing human spinal cord. Both SP- and ENK-positive fibers started to appear from the 10th week of gestation in regions surrounding the nucleus dorsalis. SP-positive fibers then reached the nucleus at 13 weeks and from 26 weeks to term, three strands of SP-positive fibers, which were predominantly originated from the superficial layers of the dorsal horn, penetrated into the nucleus dorsalis from its medial, median and lateral aspects. From 26 weeks onwards, ENK-positive fibers, originated from the superficial and the adjacent layers of the spinal cord, formed a thicker medial and a thinner lateral bundle projecting into the nucleus dorsalis. Our results show that both SP- and ENK-positive fibers started to appear at around 10 weeks and a consistent pattern of immunoreactivity was established by around 26-30 weeks of gestation.