Evaluating quality neonatal care, call Centre service, tele-health and community engagement in reducing newborn morbidity and mortality in Bungoma county, Kenya.

BACKGROUND: Neonatal mortality is a major health burden in Bungoma County with the rate estimated at 31 per 1000 live births and is above the national average of 22 per 1000. Nonetheless, out of the nine sub county hospitals, only two are fairly equipped with necessary infrastructure and skilled personnel to manage neonatal complications such as prematurity, neonatal sepsis, neonatal jaundice, birth asphyxia and respiratory distress syndrome. Additionally, with more than 50% of neonates delivered without skilled attendance, in below par hygiene environments such as home and on the roadsides, with non-existent community based referral system, the situation is made worse. The study aims to evaluate the progress made by an intervention "Collaborative Newborn Support Project" geared towards reducing neonatal mortality rate by 30% between October 2015 and December 2018 in Bungoma County, Kenya. METHODS/DESIGN: This intervention will take a quasi-experimental design approach with experimental and control sites. The project will involve pre- and post-intervention data collection with comparison group to assess intervention effects. The primary outcome will be the percentage reduction of neonatal mortality in Bungoma County. Secondary outcomes include; a) Percentage of mothers or care givers able to identify at least three danger signs in neonates in the project area, b) Proportion of neonates with complications referred to specialized neonatal centers, through the call center, c) Percentage of health providers in neonatal care units who adhere to expected neonatal standards of care (rapid and complete application of standard protocols), d) Percentage increase in neonates with severe complications in the specialized neonatal units and e) Percentage of neonates who stay in neonatal care units beyond 5 days. DISCUSSION: We outline implementation details of the ongoing 'Collaborative Newborn Support Project' in Bungoma County, Kenya. This includes strategies in the operations of the telehealth platform, call centre service, community engagement and measuring of the outputs and outcomes. The funding and ethical approvals have been obtained and the study commenced. TRIAL REGISTRATION: PACTR201712002802638 Retrospectively registered on 5th December 2017 at Pan African Clinical Trials Registry.

Skeletal complications of rheumatoid arthritis.

Rheumatoid arthritis (RA) is associated with local and systemic inflammation that induces many changes in the skeletal health. Locally, periarticular bone loss and juxta-articular bone erosions may occur while joint ankylosis, generalized bone loss, osteoporosis, and fractures may develop secondary to inflammation. The aim of this narrative review is to summarize the clinical evidence for abnormal skeletal health in RA, the effects of disease modifying anti-rheumatic drugs (DMARDS) on bone health, and the effects of drugs for the prevention or treatment of osteoporosis in the RA population.

Stillbirth rates among Indigenous and non-Indigenous women in Queensland, Australia: is the gap closing?

OBJECTIVE: To determine whether the disparity gap is closing between stillbirth rates for Indigenous and non-Indigenous women and to identify focal areas for future prevention efforts according to gestational age and geographic location. DESIGN: Population-based retrospective cohort study. SETTING: Queensland, Australia. POPULATION: All singleton births of at least 20 weeks of gestation or at least 400 g birthweight. METHODS: Routinely collected data on births were obtained for the period 1995 to 2011. Indigenous and non-Indigenous stillbirth rates and percent reduction in the gap were compared over time and by geographic location and gestational age. MAIN OUTCOME MEASURES: All-cause and cause-specific stillbirth rates (per 1000 ongoing pregnancies). RESULTS: Over the study period there was a 57.3% reduction in the disparity gap. Although marked reductions in the gap were shown for women in regional (57.0%) and remote (56.1%) locations, these women remained at increased risk compared with those in urban regions. There was no reduction for term stillbirths. Major conditions contributing to the disparity were maternal conditions (diabetes) (relative risk [RR] 3.78, 95% confidence intervals [95% CI] 2.59-5.51), perinatal infection (RR 3.70, 95% CI 2.54-5.39), spontaneous preterm birth (RR 3.08, 95% CI 2.51-3.77), hypertension (RR 2.22, 95% CI 1.45-3.39), fetal growth restriction (RR 1.78, 95% CI 1.17-2.71) and antepartum haemorrhage (RR 1.58, 95% CI 1.13-2.22). CONCLUSIONS: The gap in stillbirth rates between Indigenous and non-Indigenous women is closing, but Indigenous women continue to be at increased risk due to a number of potentially preventable conditions. There is little change in the gap at term gestational ages.

Large electric-field-induced strain in centrosymmetric crystals of a dipolar ruthenium alkynyl complex.

Dipolar molecular crystals present different physical properties from traditionally strongly correlated ionic solid-state inorganic crystals due to the weak intermolecular bonding. Herein, centrosymmetric dipolar molecular crystals of the organoruthenium complex trans-[Ru(C≡CC6H4-4-NO2)(C≡CPh)(dppe)2] [dppe = 1,2-bis(diphenylphosphino)ethane] display a large electric-field-induced strain behaving differently from conventional piezoelectric materials that must, structurally, be noncentrosymmetric. Further studies of related systematically varied crystalline organoruthenium complexes reveal that the strong electromechanical coupling effect is not from classical ferroelectricity, electrostriction, flexoelectricity or electrochemical strain. It is, instead, attributed to the disorder in the molecular packing, which facilitates reorientation of the molecular dipoles under the action of an applied electric field. This provides a fresh insight into the design and development of new functional materials and a promising source of electromechanical coupling in organometallic, and more generally dipolar molecular, crystals.

Factors Influencing Prevention and Control of Malaria among Pregnant Women Resident in Urban Slums, Southern Ghana.

Throughout Africa and particularly in Ghana, there are concerns about malaria infection during pregnancy. This study aimed to investigate factors that influence malaria prevention and control practices among pregnant women residing in Chorkor and Korle-Gonno in Accra, Ghana. One hundred and twenty pregnant women between ages 18-49 were randomly recruited during antenatal sessions at a maternity facility in Accra, as participants for the study. An interviewer-administered questionnaire was used to collect data, which were analysed using SPSS version16.0. It was found that in Chorkor and Korle-Gonno, 57.4% and 42.6% participants respectively reported having been infected with malaria during their current pregnancy. There was no significant relationship between religious beliefs of participants and their malaria prevention and control practices (X2 = 0.28, P = .53). However, there was a significant relationship between malaria prevention and control practices of participants and their income earning (X2 = 53.94, P = .00) and employment (X2 = 61.76, P = .00) statuses. With the exception of ethnicity (X2 = 35.62, P =.22), other socio-cultural conditions had a significant relationship with malaria prevention and control practices of the participants. The findings suggest the need to consider and integrate factors, such as poverty and poor living conditions in malaria prevention and control strategies.

HIV-1 drug resistance emergence among breastfeeding infants born to HIV-infected mothers during a single-arm trial of triple-antiretroviral prophylaxis for prevention of mother-to-child transmission: a secondary analysis.

BACKGROUND: Nevirapine and lamivudine given to mothers are transmitted to infants via breastfeeding in quantities sufficient to have biologic effects on the virus; this may lead to an increased risk of a breastfed infant's development of resistance to maternal antiretrovirals. The Kisumu Breastfeeding Study (KiBS), a single-arm open-label prevention of mother-to-child HIV transmission (PMTCT) trial, assessed the safety and efficacy of zidovudine, lamivudine, and either nevirapine or nelfinavir given to HIV-infected women from 34 wk gestation through 6 mo of breastfeeding. Here, we present findings from a KiBS trial secondary analysis that evaluated the emergence of maternal ARV-associated resistance among 32 HIV-infected breastfed infants. METHODS AND FINDINGS: All infants in the cohort were tested for HIV infection using DNA PCR at multiple study visits during the 24 mo of the study, and plasma RNA viral load for all HIV-PCR-positive infants was evaluated retrospectively. Specimens from mothers and infants with viral load >1,000 copies/ml were tested for HIV drug resistance mutations. Overall, 32 infants were HIV infected by 24 mo of age, and of this group, 24 (75%) infants were HIV infected by 6 mo of age. Of the 24 infants infected by 6 mo, nine were born to mothers on a nelfinavir-based regimen, whereas the remaining 15 were born to mothers on a nevirapine-based regimen. All infants were also given single-dose nevirapine within 48 hours of birth. We detected genotypic resistance mutations in none of eight infants who were HIV-PCR positive by 2 wk of age (specimens from six infants were not amplifiable), for 30% (6/20) at 6 wk, 63% (14/22) positive at 14 wk, and 67% (16/24) at 6 mo post partum. Among the 16 infants with resistance mutations by 6 mo post partum, the common mutations were M184V and K103N, conferring resistance to lamivudine and nevirapine, respectively. Genotypic resistance was detected among 9/9 (100%) and 7/15 (47%) infected infants whose mothers were on nelfinavir and nevirapine, respectively. No mutations were detected among the eight infants infected after the breastfeeding period (age 6 mo). CONCLUSIONS: Emergence of HIV drug resistance mutations in HIV-infected infants occurred between 2 wk and 6 mo post partum, most likely because of exposure to maternal ARV drugs through breast milk. Our findings may impact the choice of regimen for ARV treatment of HIV-infected breastfeeding mothers and their infected infants.

Meta-analysis and imputation identifies a 109 kb risk haplotype spanning TNFAIP3 associated with lupus nephritis and hematologic manifestations.

TNFAIP3 encodes the ubiquitin-modifying enzyme, A20, a key regulator of inflammatory signaling pathways. We previously reported association between TNFAIP3 variants and systemic lupus erythematosus (SLE). To further localize the risk variant(s), we performed a meta-analysis using genetic data available from two Caucasian case-control datasets (1453 total cases, 3381 total control subjects) and 713 SLE trio families. The best result was found at rs5029939 (P=1.67 x 10(-14), odds ratio=2.09, 95% confidence interval 1.68-2.60). We then imputed single nucleotide polymorphisms (SNPs) from the CEU Phase II HapMap using genotypes from 431 SLE cases and 2155 control subjects. Imputation identified 11 SNPs in addition to three observed SNPs, which together, defined a 109 kb SLE risk segment surrounding TNFAIP3. When evaluating whether the rs5029939 risk allele was associated with SLE clinical manifestations, we observed that heterozygous carriers of the TNFAIP3 risk allele at rs5029939 have a twofold increased risk of developing renal or hematologic manifestations compared to homozygous non-risk subjects. In summary, our study strengthens the genetic evidence that variants in the region of TNFAIP3 influence risk for SLE, particularly in patients with renal and hematologic manifestations, and narrows the risk effect to a 109 kb DNA segment that spans the TNFAIP3 gene.

Argonne intense pulsed neutron source used to solve the molecular structure of a novel organometallic complex.

The single-crystal structure of Mn(CO)(3)(C(7)H(11)) is the first to be solved by direct methods based on time-of-flight neutron diffraction data obtained at the Argonne Intense Pulsed Neutron Source. The molecule contains an unusual three-center, two-electron manganese-hydrogen-carbon interaction.

Occupational and Environmental Risk Factors Influencing the Inducement of Erythema among Nigerian Laboratory University Workers with Multiple Chemical Exposures.

: The chemicals from laboratories pose a significant risk forinducing erythema, an abnormal redness of the skin, as a result of poor occupational and environmental factors that promote hypersensitivity to a chemical agent. The aim of this present study was to determine the occupational and environmental risk factors influencing the inducement of erythema in laboratory workers due to exposure to chemicals. This was a cross-sectional study on a population-based sample of Nigerian university laboratory workers. Data were collected using the erythema index meter and an indoor air control meter. The study included 287 laboratory workers. The laboratory workers who properly used personal protective equipment (PPE) were 60% less likely to have induced erythema (adjusted odds ratio (AOR) = 0.40; 95% confidence interval CI: 0.22-0.77; probability value p = 0.011). The chemical mixture exceeding the permissible exposure limit (PEL) was found to have a small effect in inducing the erythema (AOR = 4.22; 95%CI: 2.88-12.11; p = 0.004). Most of the sampled laboratories where the respondents worked had unsuitable temperatures (AOR = 8.21; 95% CI: 4.03-15.01; p = 0.001). Erythema was more frequently found in the respondents who spent 4-5h in the laboratory (AOR = 3.11; 95%CI: 1.77-9.23; p = 0.001). However, high levels of ventilation reduce the likelihood of erythema in a laboratory by 82% (0.18). Multiple logistic regressions revealed that PPE, PEL, exposure time, temperature, and ventilation were the probable predictive factors associated with the inducement of erythema. Providing better educational knowledge and improving the attitude towards hazards and safety in a laboratory would lead to reduced rates of new cases.

Investigation of regional mechanisms responsible for poor oral absorption in humans of a modified release preparation of the alpha-adrenoreceptor antagonist, 4-amino-6,7-dimethoxy-2-(5-methanesulfonamido-1,2,3,4 tetrahydroisoquinol-2-yl)-5-(2-pyridyl)quinazoline (UK-338,003): the rational use of ex vivo intestine to predict in vivo absorption.

Modified release (MR) formulations are used to enhance the safety and compliance of existing drugs by improving their pharmacokinetics. Predicting the likely success of MR formulations is often difficult before clinical studies. A systematic in vitro approach using mouse and human tissues was adopted to rationalize the in vivo pharmacokinetics of 9- and 15-h MR formulations of an alpha-adrenoreceptor antagonist, 4-amino-6,7-dimethoxy-2-(5-methanesulfonamido-1,2,3,4 tetrahydroisoquinol-2-yl)-5-(2-pyridyl)quinazoline (UK-338,003). Immediate release UK-338,003 was well absorbed in humans consistent with moderate Caco-2 cell monolayer permeability. In contrast, 9- and 15-h modified release formulations showed marked reductions in C(max) (47.1 and 68.9%) and AUC(0-72) (32.6 and 54.0%). Colonic intubation resulted in 81.3 and 73.8% reductions in C(max) and AUC(0-72). Mechanistic studies in isolated mouse tissues showed that colonic UK-338,003 permeability (P(app) < 0.5 x 10(-6) cm/s) was at least 40 times lower than that for ileum with marked asymmetry. UK-338,003 was found to be a substrate for P-glycoprotein (PGP) with a weaker interaction for multidrug resistance-associated protein-type transporters in mouse intestine. PGP inhibition dramatically increased colonic UK-338,003 permeability to the levels observed in ileum. Low UK-338,003 apical to basolateral permeability was also observed in ex vivo human distal intestine, but both the asymmetry and increase in permeability after PGP inhibition were significantly lower. In conclusion, the poor absorption of MR UK-338,003 in humans can be explained by a combination of PGP-dependent efflux and low intrinsic permeability in the lower bowel. Regional permeability studies in ex vivo tissues used during drug development can highlight absorption problems in the distal bowel and assess the feasibility of developing successful MR formulations.

Formulation, stability and thermal analysis of lyophilised wound healing wafers containing an insoluble MMP-3 inhibitor and a non-ionic surfactant.

Lyophilised wafers are being developed as topical drug delivery systems for the treatment of chronic wounds. This study describes the formulation of xanthan wafers containing a selective, insoluble MMP-3 inhibitor (UK-370,106) and a non-ionic surfactant, designed to release accurate doses of UK-370,106 directly to a suppurating wound bed. Stability of UK-370,106 in the wafer compared to a non-lyophilised gel suspension was investigated using a combination of light scattering, thermal and microscopic techniques. Particle size distributions in UK-370,106-loaded wafers were constant throughout an accelerated stability study (12 weeks, 40 degrees C) while the mean particle size in a non-lyophilised suspension increased by 15 microm in the same period. Thermal analysis of UK-370,106-loaded wafers highlighted an unexpected interaction between the drug and the surfactant that was further investigated using simple mixtures of each component. It was concluded that an in situ solvate of UK-370,106 and the non-ionic surfactant can form and that this may have implications towards the stability of UK-370,106 during the formulation process. Further concerns regarding high water contents (14%) in the wafer and its effect on product stability were unfounded and it was concluded that these novel delivery systems provided a viable alternative to gel suspensions.

A 32-nucleotide exon-splicing enhancer regulates usage of competing 5' splice sites in a differential internal exon.

Large alternatively spliced internal exons are uncommon in vertebrate genes, and the mechanisms governing their usage are unknown. In this report, we examined alternative splicing of a 1-kb internal exon from the human caldesmon gene containing two regulated 5' splice sites that are 687 nucleotides apart. In cell lines normally splicing caldesmon RNA via utilization of the exon-internal 5' splice site, inclusion of the differential exon required a long purine-rich sequence located between the two competing 5' splice sites. This element consisted of four identical 32-nucleotide purine-rich repeats that resemble exon-splicing enhancers (ESE) identified in other genes. One 32-nucleotide repeat supported exon inclusion, repressed usage of the terminal 5' splice site, and functioned in a heterologous exon dependent on exon enhancers for inclusion, indicating that the caldesmon purine-rich sequence can be classified as an ESE. The ESE was required for utilization of the internal 5' splice site only in the presence of the competing 5' splice site and had no effect when placed downstream of the terminal 5' splice site. In the absence of the internal 5' splice site, the ESE activated a normally silent cryptic 5' splice site near the natural internal 5' splice site, indicating that the ESE stimulates upstream 5' splice site selection. We propose that the caldesmon ESE functions to regulate competition between two 5' splice sites within a differential internal exon.

A short sequence within two purine-rich enhancers determines 5' splice site specificity.

Purine-rich enhancers are exon sequences that promote inclusion of alternative exons, usually via activation of weak upstream 3' splice sites. A recently described purine-rich enhancer from the caldesmon gene has an additional activity by which it directs selection of competing 5' splice sites within an alternative exon. In this study, we have compared the caldesmon enhancer with another purine-rich enhancer from the chicken cardiac troponin T (cTNT) gene for the ability to regulate flanking splice sites. Although similar in sequence and length, the two enhancers demonstrated strikingly different specificities towards 5' splice site choice when placed between competing 5' splice sites in an internal exon. The 32-nucleotide caldesmon enhancer caused effective usage of the exon-internal 5' splice site, whereas the 30-nucleotide cTNT enhancer caused effective usage of the exon-terminal 5' splice site. Both enhancer-mediated splicing pathways represented modulation of the default pathway in which both 5' splice sites were utilized. Each enhancer is multipartite, consisting of two purine-rich sequences of a simple (GAR)n repeat interdigitated with two enhancer-specific sequences. The entire enhancer was necessary for maximal splice site selectivity; however, a 5- to 7-nucleotide region from the 3' end of each enhancer dictated splice site selectivity. Mutations that interchanged this short region of the two enhancers switched specificity. The portion of the cTNT enhancer determinative for 5' splice site selectivity was different than that shown to be maximally important for activation of a 3' splice site, suggesting that enhancer environment can have a major impact on activity. These results are the first indication that individual purine-rich enhancers can differentiate between flanking splice sites. Furthermore, localization of the specificity of splice site choice to a short region within both enhancers indicates that subtle differences in enhancer sequence can have profound effects on the splicing pathway.

Gamma-irradiation of lyophilised wound healing wafers.

Lyophilised wafers are being developed as drug delivery systems that can be applied directly to the surface of suppurating wounds. They are produced by the freeze-drying of polymer solutions and gels. This study investigates the possibility of sterilising these glassy, solid dosage forms with gamma-irradiation and determining the rheological properties of rehydrated wafers post-irradiation. One series of wafers was formulated using sodium alginate (SA) modified with increasing amounts of methylcellulose (MC), the other being composed of xanthan gum (XG) and MC. Batches were divided into three lots, two of which were exposed to 25 and 40 kGrays (kGy) of Cobalt-60 gamma-irradiation, respectively, the third being retained as a non-irradiated control. Apparent viscosities of solutions/gels resulting from the volumetric addition of distilled water to individual wafers were determined using continuous shear, flow-rheometry. Flow behaviour on proprietary suppurating surfaces was also determined. Large reductions in viscosity were apparent for irradiated SA samples while those of XG appeared to be largely unaffected. In addition, an increase in the yield stress of xanthan formulations was observed. Xanthan wafers appeared to withstand large doses of irradiation with no detrimental effect on the rheology of reconstituted gels. This offers the possibility of manufacturing sterilisable delivery systems for wounds.

Lyophilised wafers as a drug delivery system for wound healing containing methylcellulose as a viscosity modifier.

Lyophilised wafers have potential as drug delivery systems for suppurating wounds. A dual series of wafers made from low molecular weight sodium alginate (SA) and xanthan gum (XG) respectively, modified with high molecular weight methylcellulose (MC) were produced. The swelling and flow properties of these wafers on model suppurating surfaces were both qualitatively and quantitatively investigated. The wafers instantaneously adhered to the surfaces, absorbing water and transforming from glassy, porous solids to highly viscous gels. The rate at which this occurred varied for the series studied with clear distinctions between the behaviour of SA and XG systems. For SA wafers there was a distinct relationship between the flow-rate and MC content. Increased amounts of MC decreased the rate at which the SA wafers flowed across a model gelatine surface. Flow rheometry was used to quantify the effect of increased MC content on both series of wafers and for the SA series, highlighted a substantial increase in apparent viscosity as a function of incremental increases in MC content. These results reflected those from the gelatine model. Observations of the reluctance of a swollen, unmodified XG wafer to flow compared with the relative ease of unmodified, low molecular weight SA was attributed to the yield stress characteristic of xanthan gels. XG is known to exhibit complex, loosely bound network structures in solution via the association of helical backbone structures. The inclusion of sodium fluorescein as a visible model for a soluble drug highlighted the potential of lyophilised wafers as useful drug delivery systems for suppurating wounds.

Cloning of cDNAs encoding human caldesmons.

Caldesmon (CDM) is a potential actomyosin regulatory protein found in smooth muscle and nonmuscle cells. Domain mapping and physical studies suggest that CDM is an elongated molecule with an N-terminal myosin/calmodulin-binding domain and a C-terminal tropomyosin/actin/calmodulin-binding domain separated by a 40-nm-long central helix. An 1100-nucleotide (nt) cDNA probe encoding the C terminus of avian caldesmon (aCDM) was used to screen a human aorta library and clone smooth-muscle and non-muscle CDM-encoding cDNAs (CDM). The human (h) smooth-muscle hCDM is 3050-3630 nt long, having variation in length in the 3'-untranslated region. The predicted hCDM protein has a high degree of identity, greater than 90%, to aCDM in the N- and C-terminal-binding domains. The central helical domain is more variable, but retains characteristic repeated peptides and an 'i, i + 4' acidic/basic amino acid (aa) motif found in aCDM which can form intra-helical salt bridges to stabilize the central helix. The predicted smooth-muscle protein is 793 aa long (93,262 Da) with a calculated pI of 5.75. As is the case for the chicken, nonmuscle hCDM is missing the central helical domain, 256 aa overall. Our nonmuscle clone is not full length, but the C-terminal end is identical to the smooth-muscle form. If the N-terminal domain is identical, as it is in the chicken, the predicted protein is 537 aa (62,558 Da). Examination of the 'junctions' at either end of the deleted central domain gives a clear indication of the splice sites and suggests that the nonmuscle form is generated by exon skipping.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of different optic nerve lesions on retinal ganglion cell death in the frog Rana pipiens.

Following optic nerve crush in various species of frog, a proportion of the retinal ganglion cells re-establishes functional contact with the optic tectum. However, as much as 50% of the retinal ganglion cells die during this process. The determinants of an individual ganglion cell's fate have not been established. In this study of Rana pipiens, cell survival after optic nerve crush was compared with that after nerve cut followed by stump separation, a procedure that considerably delayed entry of optic axons to the brain. It was also ascertained, in the case of delayed ingrowth, whether application of nerve growth factor immediately after lesion influenced the cell death process. This study confirmed that retinal ganglion cell death is a relatively late event in regeneration, because in several animals where anterograde HRP labeling demonstrated regenerating axons within the tectum, no cell death had occurred. There was no statistically significant difference in cell death at 75 days after lesion between animals receiving nerve crush and those receiving nerve cut with stump separation, even though most crush animals had regenerated a complete visual projection, whereas most nerve cut animals had not. The application of NGF did not influence the level of cell death at 75 days after lesion. These results suggest that contact of optic axons with the optic tract or tectum is not necessary for retinal ganglion cell death to occur. However, this does not necessarily mean that contact with the brain is not involved with cell death during regeneration following nerve crush because it is possible that the mechanisms of cell death are different when axons are prevented from regenerating. Further investigations are therefore required to establish the reasons for this cell death.

Retinal ganglion cell death during optic nerve regeneration in the frog Hyla moorei.

In the frog Hyla moorei we have estimated there to be between approximately 450,000 and 750,000 cells in the retinal ganglion cell layer. Optic axon counts and retrograde transport of horseradish peroxidase (HRP) indicated that 72-76% of these were ganglion cells. Cells of this type were distributed as a temporally situated area centralis within a horizontal visual streak. Cell and optic axon counts showed that there was an approximately 40% loss of ganglion cells during optic nerve regeneration. Ganglion cells appeared chromatolysed by 6-8 days after an extracranial nerve crush but there was no indication of cell death until 15 days. By this stage anterograde transport of HRP indicated that axons had reached the chiasma. Death was first seen in the area centralis, extended along the streak, and finally was observed in the periphery by 65 days; cell counts demonstrated that at this time the wave of death was almost complete. We have previously shown by electrophysiological visual mapping (Humphrey and Beazley, '82) and confirmed in this study that visuotectal projections were retinotopically organized during regeneration. Multiunit receptive fields were initially large but progressively refined starting in nasal field (temporal retina) to restore a normal projection. The similar sequences whereby the visuotectal projection became refined and death took place in the retinal ganglion cell layer suggested that death may be related to a process of organization within the regenerating projection. In normal animals primary visual pathways revealed by anterograde transport of HRP were essentially similar to those of Rana pipiens and R. esculenta. Regenerating axons generally remained within optic pathways. Exceptions were a retinoretinal projection which was not completely withdrawn even after 1,028 days and a direct projection to the ipsilateral tectum via an inappropriate part of the optic tract.

A quantitative study of the lateral spread of Müller cell responses to retinal lesions in the rabbit.

A wide variety of retinal pathology is associated with an increase in Müller glial cell expression of glial fibrillary acidic protein (GFAP). In this study the time course and spatial spread of the Müller cell GFAP response following argon laser photocoagulation lesions was examined in wholemounted rabbit retina. At 24 hours single focal lesions were surrounded by GFAP positive Müller cell end feet which declined in density with distance but extended as far as 2-3 mm from the lesion. The Müller cell reaction reached a maximal spread of 4-5 mm at 14 to 21 days and had started to contract by 30 days, leaving a core of GFAP positive processes immediately around the lesion site at 60 days. This zone of spread was much larger than the area of disrupted pigment epithelium. Isodensity plots did not reveal any correlation with the trajectory of retinal ganglion cell axons. The spread of reaction was more confined for lesions within the visual streak than in the dorsal or ventral retinal periphery. Multiple lesions within a focal region of retina resulted in a greater density of GFAP reactive end feet with a corresponding greater spread. However, when five to ten lesions were made in a horizontal row, the Müller cells over the entire retina became GFAP immunoreactive. This pan-retinal reaction took several days to spread, peaked at 7-14 days, and contracted back to the primary lesion sites by 2 months. This spread of Müller cell reactivity may be triggered by the diffusion of substances released by injury or it may be due to direct cellular communication. The extensive indirect effect on Müller cells of laser irradiation might be an important component of the clinical effect of laser photocoagulation and indicates a long distance communication mechanism between retinal glia which is poorly understood. This study also shows the importance of the time at which the Müller cell response is assessed.