Visual system evolution and the nature of the ancestral snake.

The dominant hypothesis for the evolutionary origin of snakes from 'lizards' (non-snake squamates) is that stem snakes acquired many snake features while passing through a profound burrowing (fossorial) phase. To investigate this, we examined the visual pigments and their encoding opsin genes in a range of squamate reptiles, focusing on fossorial lizards and snakes. We sequenced opsin transcripts isolated from retinal cDNA and used microspectrophotometry to measure directly the spectral absorbance of the photoreceptor visual pigments in a subset of samples. In snakes, but not lizards, dedicated fossoriality (as in Scolecophidia and the alethinophidian Anilius scytale) corresponds with loss of all visual opsins other than RH1 (λmax 490-497 nm); all other snakes (including less dedicated burrowers) also have functional sws1 and lws opsin genes. In contrast, the retinas of all lizards sampled, even highly fossorial amphisbaenians with reduced eyes, express functional lws, sws1, sws2 and rh1 genes, and most also express rh2 (i.e. they express all five of the visual opsin genes present in the ancestral vertebrate). Our evidence of visual pigment complements suggests that the visual system of stem snakes was partly reduced, with two (RH2 and SWS2) of the ancestral vertebrate visual pigments being eliminated, but that this did not extend to the extreme additional loss of SWS1 and LWS that subsequently occurred (probably independently) in highly fossorial extant scolecophidians and A. scytale. We therefore consider it unlikely that the ancestral snake was as fossorial as extant scolecophidians, whether or not the latter are para- or monophyletic.

Comparative electron microscopy study of spermatozoa in snakes (Lepidosauria, Squamata).

The ultrastructure of snake sperm has received substantial attention primarily because snakes exhibit considerable variability in reproductive characteristics between species, with a wide range of mating systems and reproductive behaviors. Variability of sperm morphology among snake species may be associated with the reproductive strategies of each taxon, such as competition or sperm storage. We provide a detailed description of the sperm ultrastructure of nine snake species (Anilius scytale, Tropidophis paucisquamis, Bothrops jararaca, Oxyrhopus guibei, Dipsas mikanii, Micrurus corallinus, Xenopholis scalaris, Acrochordus javanicus, and Cylindrophis ruffus) and compared this with sperm data from the literature for the following taxa: Liotyphlops beui, Amerotyphlops reticulatus, Trilepida koppesi, Anilios waitii, Anilios endoterus, Aspidites melanochephalus, Boa constrictor amarali, Corallus hortulana, Epicrates cenchria, Boa constrictor occidentalis, Eryx jayakari, Micrurus corallinus, Micrurus surinamensis, Micrurus frontalis, Micrurus altirostris, Oxyuranus microlepidotus, Bothrops alternatus, Bothrops diporus, Crotalus durissus, Agkistrodon contortrix, Vipera aspis, Boiga irregularis, Zamenis schrenckii, Zamenis scalaris, Stegonotus cuculatus, Nerodia sipedon, Liodytes pygaea, and Myrrophis chinensis. We found twelve polymorphic characters in the ultrastructure of sperm among the described snakes. Our work supports the importance of ultrastructural analysis of sperm morphology to understand snake reproduction, and provides sperm-derived morphological characters for phylogenetic analysis.

Batrachochytrium dendrobatidis in amphibians of Cameroon, including first records for caecilians.

Amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) has been hypothesised to be an indigenous parasite of African amphibians. In Cameroon, however, previous surveys in one region (in the northwest) failed to detect this pathogen, despite the earliest African Bd having been recorded from a frog in eastern Cameroon, plus one recent record in the far southeast. To reconcile these contrasting results, we present survey data from 12 localities across 6 regions of Cameroon from anurans (n = 1052) and caecilians (n = 85) of ca. 108 species. Bd was detected in 124 amphibian hosts at 7 localities, including Mt. Oku, Mt. Cameroon, Mt. Manengouba and lowland localities in the centre and west of the country. None of the hosts were observed dead or dying. Infected amphibian hosts were not detected in other localities in the south and eastern rainforest belt. Infection occurred in both anurans and caecilians, making this the first reported case of infection in the latter order (Gymnophiona) of amphibians. There was no significant difference between prevalence and infection intensity in frogs and caecilians. We highlight the importance of taking into account the inhibition of diagnostic qPCR in studies on Bd, based on all Bd-positive hosts being undetected when screened without bovine serum albumin in the qPCR mix. The status of Bd as an indigenous, cosmopolitan amphibian parasite in Africa, including Cameroon, is supported by this work. Isolating and sequencing strains of Bd from Cameroon should now be a priority. Longitudinal host population monitoring will be required to determine the effects, if any, of the infection on amphibians in Cameroon.

High-Density Geometric Morphometric Analysis of Intraspecific Cranial Integration in the Barred Grass Snake (Natrix helvetica) and Green Anole (Anolis carolinensis).

How do phenotypic associations intrinsic to an organism, such as developmental and mechanical processes, direct morphological evolution? Comparisons of intraspecific and clade-wide patterns of phenotypic covariation could inform how population-level trends ultimately dictate macroevolutionary changes. However, most studies have focused on analyzing integration and modularity either at macroevolutionary or intraspecific levels, without a shared analytical framework unifying these temporal scales. In this study, we investigate the intraspecific patterns of cranial integration in two squamate species: Natrix helvetica and Anolis carolinensis. We analyze their cranial integration patterns using the same high-density three-dimensional geometric morphometric approach used in a prior squamate-wide evolutionary study. Our results indicate that Natrix and Anolis exhibit shared intraspecific cranial integration patterns, with some differences, including a more integrated rostrum in the latter. Notably, these differences in intraspecific patterns correspond to their respective interspecific patterns in snakes and lizards, with few exceptions. These results suggest that interspecific patterns of cranial integration reflect intraspecific patterns. Hence, our study suggests that the phenotypic associations that direct morphological variation within species extend across micro- and macroevolutionary levels, bridging these two scales.

The Karyology of Uraeotyphlus gansi, and Its Implications for the Systematics and Evolution of Uraeotyphlidae (Amphibia: Gymnophiona).

The gross karyotype of the uraeotyphlid caecilian Uraeotyphlus gansi is described as comprising 2n = 42 and fundamental number = 58. These are the first karyotype data for any species of malabaricus-group Uraeotyphlus, and the diploid number is the same as those ichthyophiids thus far studied and differs from the oxyurus-group Uraeotyphlus (2n = 36). These data support the recognition of two species groups within Uraeotyphlus, the monophyly of the oxyurus group, and the understanding that the ancestral diatriatan was more ichthyophiid- than uraeotyphlid-like.

Identification and characterization of visual pigments in caecilians (Amphibia: Gymnophiona), an order of limbless vertebrates with rudimentary eyes.

In comparison with the other amphibian orders, the Anura (frogs) and Urodela (salamanders), knowledge of the visual system of the snake-like Gymnophiona (caecilians) is relatively sparse. Most caecilians are fossorial with, as far as is known any surface activity occurring mainly at night. They have relatively small, poorly developed eyes and might be expected to possess detectable changes in the spectral sensitivity of their visual pigments. Microspectrophotometry was used to determine the spectral sensitivities of the photoreceptors in three species of caecilian, Rhinatrema bivittatum, Geotrypetes seraphini and Typhlonectes natans. Only rod opsin visual pigment, which may be associated with scotopic (dim light) vision when accompanied by other 'rod-specific' components of the phototransduction cascade, was found to be present. Opsin sequences were obtained from the eyes of two species of caecilian, Ichthyophis cf. kohtaoensis and T. natans. These rod opsins were regenerated in vitro with 11-cis retinal to give pigments with spectral sensitivity peaks close to 500 nm. No evidence for cone photoreception, associated with diurnal and colour vision, was detected using molecular and physiological methods. Additionally, visual pigments are short-wavelength shifted in terms of the maximum absorption of light when compared with other amphibian lineages.

Hyperthermia protects against light damage in the rat retina.

An increase in the synthesis of heat shock proteins that is induced in cells in vitro by hyperthermia or other types of metabolic stress correlates with enhanced cell survival upon further stress. To determine if a similar increase in stress tolerance could be elicited in vivo, rats were made hyperthermic, and then their retinas were tested for sensitivity to light damage. This treatment resulted in a marked decrease in photoreceptor degeneration after exposure to bright light as compared to normothermic animals. Concomitant with such protection was an increase in retinal synthesis of three heat shock proteins. Thus, a physiological rise in body temperature enhances the stress tolerance of nerve tissue, perhaps by increasing heat shock protein production.

Frequency of independent origins of viviparity among caecilians (Gymnophiona): evidence from the first 'live-bearing' Asian amphibian.

Viviparity is reported for Gegeneophis seshachari (Gymnophiona: Caeciliidae) from a gravid female containing four oviductal foetuses. The oviducts are highly vascularized and contain patches of thickened, layered tissue similar to foetal gut contents. Gegeneophis seshachari probably resemble other viviparous caecilians in having foetuses that ingest thickened oviduct lining using specialized deciduous teeth. This is the first report of viviparity in Asian amphibians and Indo-Seychellean caeciliids. Gegeneophis is the only caecilian genus known to include oviparous and viviparous species, and G. seshachari is the smallest known viviparous caecilian. Phylogenetic analysis of mitochondrial DNA sequences supports assignment of G. seshachari to a monophyletic Gegeneophis. Character optimization indicates that viviparity has evolved independently at least four times within Gymnophiona--a rate of incidence relative to the number of extant species that is higher than for other vertebrate groups except squamate reptiles. Our findings strengthen the proposal that caecilian reproduction demands further attention.

Axonal transport of clathrin-associated proteins.

Clathrin, the main constituent of coated vesicles, is anterogradely transported exclusively in the slow component b (SCb) of axonal transport. However, it has not been shown whether the 30-36-kDa clathrin-associated proteins (CAPs), which may regulate assembly of clathrin into coated vesicles, are transported along with clathrin in SCb. Clarification of this point has implications for the functional state of anterogradely transported clathrin. To investigate CAPs transport, retinal ganglion cells of the guinea pig were labeled with 35S-methionine and the optic nerves harvested at 6 h, 4 days, and 30 days to collect radiolabeled proteins from each major rate component of axonal fast component (FC), slow component a (SCa), and SCb. The radiolabeled rate component proteins were analyzed by using two-dimensional polyacrylamide gel electrophoresis and fluorography. The results showed that CAPs, like clathrin, were transported exclusively with the proteins of SCb. In addition, a comparison of radiolabeled CAPs isolated from axons with whole-brain CAPs failed to demonstrate an appreciable difference in molecular weight or isoelectric point between the two, suggesting that CAPs did not undergo a major post translational modification upon passage into the synaptic terminal. It appears that the distinctive microenvironment within the synaptic terminal is likely to contribute to the ability of clathrin and CAPs to interact with membranes.

Water deprivation protects photoreceptors against light damage.

Photoreceptor cell death after light-damage and during aging in rats is associated with the hormonal status of the animal, as well as other environmental and intrinsic factors. Restricted caloric intake extends the life of rodents and is usually accompanied by a reduction in water consumption. In this study, male and female rats were placed on restricted water intake for either 3 or 7 days to induce dehydration. Following exposure to damaging visible light, the retinas were evaluated for severity of damage and photoreceptor survival, heat shock (stress) protein (HSP) and total protein synthesis, and plasma arginine vasopressin (AVP) levels. Photoreceptor cells of 7-day, dehydrated male and female rats survived light-damage significantly better than those allowed water ad libitum; however, after 3 days of water restriction, only the male rats demonstrated protection from photodamage. Severity of photoreceptor damage could not be correlated with retinal HSP synthesis and content, although the latter was significantly reduced in dehydrated animals. Total retinal protein content and synthesis were unchanged by restricted water intake. AVP increased by 350% during the 7-day period of dehydration. Protection of photoreceptors from light-damage in this study may be correlated with osmotically stimulated changes in the retinas of dehydrated animals.

Slow axonal protein transport and axoplasmic organization.

A recently formulated structural theory of axonal transport suggests that each group of transported material is a distinct class of functionally related structures and that the proteins making up those structures, with few exceptions, are found in only one rate component, thus maintaining a close noncovalent association during transport. If such a relationship exists, one would postulate that the labelled proteins at the leading edge and trailing edge of a rate component following a pulse of radioactive amino acid would be present in similar proportions. After retinal ganglion cell proteins were labelled by intraocular injection of radioactive amino acid in the guinea pig eye, the optic nerve and tract were analyzed at several post-injection intervals. The data thus derived support the existence of a close relationship among the "soluble" proteins of slow component b and are consistent with the structural concept of axonal transport. If diffusion were the mechanism of transport, the larger proteins would be expected to move slower than the smaller proteins. Such insights into the process of axonal transport should help to identify the variables critical to survival of neurons following acute trauma and degenerative diseases.

e-PTFE ventricular shunt catheters.

The perfect polymer surface for implantation should resist the adhesion of bacteria while producing no reaction in surrounding tissues. Silicone elastomer is a common material used for medical implantation devices. This material is superior to most available for implantation because of its flexibility and low, but detectable, tissue reaction. We have evaluated a flexible, expanded polytetrafluoroethylene (e-PTFE) ventricular catheter for cerebrospinal fluid shunting and have found that although e-PTFE is safe for cerebral implantation, the porosity of the material allows tissue ingrowth that obstructs the lumen. Our limited clinical evaluation of 5-microns internodal distance e-PTFE revealed that this open-cell structure, allowing tissue ingrowth, apparently is a poor candidate to replace silicone elastomer in cerebrospinal fluid shunting devices. However, further investigation may provide a polymer superior to silicone elastomer to create a cerebrospinal fluid shunt.

Enlarging endostoma (bone island) of the spinous process.

Endostoma of bone (bone island) is a rare lesion and has been described in the spinous process in only one previous publication. Although these lesions are benign, they have a potential for enlargement. Radiography cannot completely differentiate these lesions from more aggressive processes, and removal of the lesion should be considered.

Candida albicans shunt infection: report of two cases.

Infection of cerebrospinal fluid shunts with Candida albicans is reported in two patients. Scanning electron microscopy in one case demonstrates the relationship of the Candida hyphae to the white blood cells and to silicone plastic. A review of 10 previously reported cases of Candida shunt infection indicates that the infection usually follows a major bacterial infection or direct contamination or occurs spontaneously. Previous therapy has usually involved removal of the shunt, and the role of parenteral antifungal therapy is still unclear. Overall mortality to date is 25%.

Role of subtemporal decompression in severe closed head injury.

There is general agreement that aggressive management and monitoring of the patient with closed head injury with control of intracranial pressure (ICP) will improve patient survival and eventual outcome. Conversely, there is little agreement on the value of surgical craniectomy for increasing intracranial volume and subsequently decreasing ICP in these same patients. This study examines 115 patients with severe closed head injuries (Glasgow Coma Score 8 or less) seen at the North Carolina Baptist Hospital between July 1, 1983, and April 1, 1987. All 115 patients were started on a regimen of head elevation, fluid restriction, chemoparalysis, and hyperventilation at PCO2 25-30 torr. Fifty-seven patients failed to respond to that therapy and were given mannitol. Twenty-seven of these still failed to respond; 24 were placed in a pentobarbital coma therapy group and 3 underwent subtemporal decompression. Of the 24 patients in pentobarbital coma, 17 failed to respond, 7 of whom underwent subtemporal decompression and 10 of whom were not operated on. Of all 10 patients undergoing subtemporal decompression, 7 (70%) responded with an average reduction in ICP of 34% (+/- 19.5% SD). Of the 10, 4 died (40%), in contrast with a mortality of 82.4% among patients in pentobarbital coma without subtemporal decompression. These data strongly suggest that subtemporal decompression can be beneficial in patients with medically intractable elevations of ICP.

Aneurysm of the superficial temporal artery.

A young patient with the posttraumatic development of a superficial temporal artery (STA) aneurysm is described. The STA was ligated proximal and distal to the aneurysm, and the aneurysm was removed. The diagnosis and treatment of traumatic STA aneurysms are discussed.

Cystic optic glioma.

A pilocytic astrocytoma of the optic nerve, chiasm, hypothalamus, or third ventricle is a relatively common tumor of childhood. This case report illustrates such a tumor, originating from this location, which is unusual because of the association with two very large cystic extensions into the middle cranial fossa and into the third ventricle. The massive size and extent of this tumor and cysts was demonstrated on a magnetic resonance imaging (MRI) scan, with gadolinium enhancement. This case illustrates a novel macroscopic appearance for a pilocytic glioma of the anterior third ventricle. The purpose of this report is to alert clinicians to the varied morphology this tumor may present as we apply increasingly our improved radiological, operative, and histopathological techniques.

Changing concepts in spinal epidural abscess: a report of 29 cases.

A review of our recent experience with spinal epidural abscess (SEA) reveals several important changing concepts in diagnosis, etiology, management, and outcome. All cases of SEA seen by our service from August 1975 to July 1989 were reviewed retrospectively, and 29 patients were identified (19 men and 10 women, aged 13-78 years). Abscesses were located in the lumbar (n = 21), thoracic (n = 7), and cervical (n = 1) epidural spaces. Gram-positive organisms were the infectious agent in 72% of the cases, and Staphylococcus aureus was the sole agent in 45%; other agents were Gram-negative aerobes (n = 5), a Gram-negative anaerobe (n = 1), Mycobacterium tuberculosis (n = 1), and Sporotrichum schenckii (n = 1), the last occurring in a young woman with acquired immune deficiency syndrome. Seventeen patients had concomitant extraspinal infections. Diagnosis was confirmed by myelography, computed tomography, or magnetic resonance imaging. All patients underwent operative decompression and debridement; 2 required a second procedure for persistent infection. The most common operative findings were pus and granulation tissue in the epidural space (52%); the preoperative course correlated poorly with operative findings. The wound was closed primarily in 84% of cases. Postoperative intravenous antibiotic courses for the bacterial abscesses ranged from 1.5 to 6 weeks (median, 2 weeks), followed by antibiotics given orally for 0 to 6 weeks. Two patients died perioperatively. Neurological outcome was good in 21 patients and fair in 6 (mean follow-up, 1.4 years). Over the last 50 years the spectrum of organisms causing SEA has broadened, and the distinction between acute and chronic SEAs has minimal clinical significance.(ABSTRACT TRUNCATED AT 250 WORDS)

Carotid plaque as a source of emboli in humans: a scanning electron microscopic study.

Ten fresh carotid plaques obtained from patients undergoing carotid endarterectomy were fixed, and their luminal surfaces were examined with a scanning electron microscope. Luminal surface defects, characterized in scanning electron microscopy as endothelial discontinuities having diameters of 50 to 1500 microns, were a frequent finding, but their presence did not correlate well with the location of ulcers seen on angiography. Potential sources of emboli found were peels of subendothelial matrix, fibrin-platelet aggregates, fibrin-red blood cell clusters, and, possibly, damaged endothelial cells. Areas of endothelial cell injury consisting of small denuded patches, sheets of endothelial cytoplasm, and distorted endothelial cell profiles were observed. These areas resembled the type of damage seen in experimental ischemic vessel lesions and were believed to be the result of carotid cross clamping. Their presence suggests that a similar mechanism may result in loss of endothelial cells and exposure of the "raw" plaque surface in vivo.

Spinal cord injury and the stress protein response.

The heat shock or stress response is a highly conserved primary cellular response to injury. Synthesis of stress proteins (also called "heat shock proteins") is an integral component of this response. Protection from various forms of sublethal stress following increased production of stress proteins has been demonstrated in a number of systems, including the retina. This immunocytochemical study demonstrates the synthesis, accumulation, and redistribution of the 70-kD stress protein following spinal cord injury in rats. The observations confirm that stress protein production is a fundamental feature of the molecular response of the spinal cord to injury, and raise the possibility that augmentation of this response could enhance posttraumatic neuronal survival.