Blind spot size depends on the optic disc topography: a study using SLO controlled scotometry and the Heidelberg retina tomograph

AIMS—To find out whether the size of the blind spot area, determined by static perimetry, depends on the surface topography of the optic disc and its surrounding area.
METHODS—Ten eyes were examined; all had a parapapillary atrophy adjacent to the temporal side of the disc. Microperimetry was performed under direct fundus control using a Rodenstock scanning laser ophthalmoscope. The horizontal meridian of the optic discs was examined in 0.5° steps using five stimulus sizes (Goldmann I to V), each with 10 different degrees of brightness. Optic disc topography was measured with the Heidelberg retina tomograph (HRT).
RESULTS—Stimuli with a high luminance level (Goldmann IV, 4 dB), presented on the horizontal meridian, were seen up to 0.75° centrally (that is, towards the optic disc centre) from the temporal edge of the parapapillary atrophy but up to 1.85° centrally from the nasal optic disc border (p<0.01). Horizontal HRT section profiles of the optic disc consistently showed prominent nasal disc borders contrasting with a shallow excavation within the temporal parapapillary atrophy.
CONCLUSIONS—The size of scotomas depends on the surface topography of the tested area. The prominent nasal part of the optic disc appears less `blind' than the shallow temporal part, probably because of more intensive light scattering by the prominent nasal part of the disc. These considerations should also apply to other scotomas.

     

Evaluation of three substitutes for Percoll in sperm isolation by density gradient centrifugation

Silane-coated silica particle solutions (ISolate(TM) and PureSperm)TM)) and iodixanol (OptiPrep(TM)) were compared to polyvinylpyrrolidone (PVP)-coated silica particles (Percoll(TM)) in their efficacy to recover spermatozoa by gradient centrifugation for use in assisted reproductive procedures. Efficacy was assessed in terms of percentages of sperm recovery, sperm vitality and motility, normal sperm morphology and normal sperm chromatin condensation. No significant difference was found in the recovery of spermatozoa for men with both normal sperm counts and oligozoospermia, between PVP-coated and silane-coated particle solutions. Iodixanol had significantly lower sperm recovery compared to the other products. Sperm vitality, progressive motility, normal morphology and normal chromatin condensation did not differ significantly between any of the sperm isolation products.      

Immunohistochemical localization of the differentiation marker E11 in dental development of rats

E11 antigen, originally characterized in a rat osteosarcoma cell line, is known to be expressed during late stages of the osteogenic cell lineage both in vitro and in vivo. The aim of the present study was to monitor the occurrence and distribution patterns of the E11 antigen using monoclonal antibodies (mAb E11 and MEP-1) during different stages of tooth germ development of new-born rats by means of immunohistochemistry. Both antibodies strongly bound to plasma membranes of ameloblasts in presecretory and secretory stages. In addition, odontoblasts and cells of the periodontium were immunoreactive for E11 and MEP-1. During maturation, the immunoreactivity of ameloblast plasma membranes decreased significantly. Our data suggest that E11 and MEP-1 might be important as markers for cell differentiation and mineralization processes during tooth germ development.     

Natural rhythm: evidence for occult 40 Hz gamma oscillation in resting motor cortex

Fast gamma oscillations, often at 40 Hz, have been demonstrated throughout the brain including the thalamus, auditory, visual and motor cortices. The function of gamma rhythms is elusive, but several authors have hypothesized that they contribute to the "binding" of diverse information into a single coherent percept, and to the synchronization of movement. In skeletal muscle a "Piper rhythm" around 40 Hz is commonly observed during maximal voluntary contraction, and has been shown to correlate with activity of similar frequency in a limited area of contralateral motor cortex. Gamma rhythms are detected primarily during complex cortical activity, and are seldom recorded at rest or coherently over wide areas. Here we use bihemispheric transcranial magnetic stimulation (TMS) to study time-dependent correlations between evoked motor potentials from non-homologous muscles in opposite limbs of normal volunteers. The results suggest the presence of an occult, synchronous 40 Hz rhythm across broad areas of resting motor cortex in both hemispheres.     

Cloning of a gene involved in regulation of exotoxin A expression in Pseudomonas aeruginosa.

We have cloned a gene from Pseudomonas aeruginosa that stimulates the expression of exotoxin A. A recombinant library of genomic DNA from strain PA103 constructed with a broad-host-range plasmid vector containing chromosomal insert fragments generated by Sau3A was used to transform the hypotoxigenic mutant strain PA103-29. A recombinant plasmid, pFHK6, was isolated from a PA103-29 transformant which displayed increased toxin production. From pFHK6, which contained a 20-kilobase-pair chromosomal insert, a 3-kilobase-pair XhoI fragment was isolated and subcloned into the plasmid cloning vector pVK101 to give pFHK10. In toxigenic P. aeruginosa strains containing pFHK10, toxin expression was increased 10-fold and high levels of iron in the culture medium only partially inhibited the overproduction. Expression studies suggested that pFHK10 did not contain the toxin structural gene. In addition, Southern analysis with the 3-kilobase-pair XhoI fragment suggested that the putative toxin regulatory gene is common among different strains of P. aeruginosa including previously reported nontoxigenic strains.     

Inhibition of CDK activity and PCNA-dependent DNA replication by p21 is blocked by interaction with the HPV-16 E7 oncoprotein

p21 inhibits cyclin-dependent kinase (CDK) activity and proliferating cell nuclear antigen (PCNA)-dependent DNA replication by binding to CDK/cyclin complexes and to PCNA through distinct domains. The human papillomavirus (HPV)-16 E7 oncoprotein (16E7) abrogated a DNA damage-induced cell cycle arrest in vivo, despite high levels of p21. Using cell lysates and purified proteins we show that 16E7 prevented p21 both from inhibiting CDK2/cyclin E activity and PCNA-dependent DNA replication, whereas the nononcogenic HPV-6 E7 had reduced effects. Inactivation of both inhibitory functions of p21 was attained through binding between 16E7 and sequences in the carboxy-terminal end of p21 that overlap with the PCNA-binding site and the second p21 cyclin-binding motif. These data imply that the carboxyl terminus of p21 simultaneously modulates both CDK activity and PCNA-dependent DNA replication and that a single protein, 16E7, can override this modulation to disrupt normal cell cycle control.     

Antimicrobial resistance of Salmonella isolates from swine

We examined the antimicrobial resistance of 1,257 isolates of 30 serovars of Salmonella enterica subsp. enterica isolated from swine. Serovars Typhimurium and Typhimurium var. Copenhagen were widespread and were frequently multidrug resistant, with distinct resistance to ampicillin, kanamycin, streptomycin, sulfamethoxazole, and tetracycline and to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline, respectively.     

Acute nicotine enhances c-fos mRNA expression differentially in reward-related substrates of adolescent and adult rat brain

A number of studies have demonstrated that adolescent rodents are more sensitive to the rewarding effects of nicotine compared to adults. To help determine the potential brain circuitry involved, we investigated the effect of acute nicotine administration (0.4 or 0.8 mg/kg, s.c.) on the expression of c-fos mRNA in the brains of adolescent (P35) and adult (P67-70) male Wistar rats using in situ hybridization. Nicotine administration increased c-fos mRNA expression in several brain regions, including the central amygdala, locus coeruleus, nucleus accumbens core, paraventricular nucleus of the hypothalamus and lateral septum of adolescent and adult rats. Nicotine increased c-fos mRNA expression more robustly in the bed nucleus of the stria terminalis, nucleus accumbens shell and ventral tegmental area in adolescent rats. The current results suggest that nicotine may have greater activational effects in brain regions associated with reward in adolescent rats and may help to explain the differences between adolescents and adults in behavioral responses to nicotine.     

Smoking and Drinking Behavior in Patients with Head and Neck Cancer: Effects of Behavioral Self-Blame and Perceived Control

Patients who continue to use tobacco or alcohol following treatment for head and neck cancers are at greater risk for cancer recurrence and mortality. The present study examined the effects of behavioral self-blame and perceived control over health on smoking and alcohol use in a sample of 55 patients with cancers of the head and neck. Measures of self-blame, perceived control, and depression were administered and an assessment of past and current smoking and drinking behavior was obtained. As anticipated, continued smoking after completion of oncologic treatment was predicted by the interaction of behavior specific self-blame and perceived control. Patients who attributed the cause of their cancer to their past substance use exhibited a lower likelihood of smoking only if they also held the expectancy that their future cancer-related health was contingent on their own behavior. Among patients not holding the belief that cancer recurrence was contingent on their own actions, self-blame was associated with a higher probability of continued smoking. Self-blame and perceived control had no effect on continued alcohol use.     

Induction of apoptosis by glyoxal in human embryonic lung epithelial cell line L132

Oxidative stress has been suggested to play a central role in the pathogenesis of lung fibrosis and lung epithelial cell apoptosis is considered to be a key event during fibrogenesis. Studies from various laboratories have indicated that metabolic conditions may initiate oxidative stress, thereby contributing to epithelial cell death. This study was designed to test the hypothesis that glyoxal, an intermediate product in the glycation reaction leading to advanced glycation end products (AGEs), may induce lung epithelial cell apoptosis. We investigated the in vitro effects of glyoxal on fetal human lung epithelial L132 cells. Immunocytochemical analysis of paraffin-embedded cells and fluorescence-activated cell sorter analysis revealed a dose-dependent accumulation of the glycoxidation product (epsilon)N-carboxymethyllysine (CML) in all compartments of the cell. It has been shown that CML modification of proteins may serve as an indicator for oxidative stress. To examine the role of apoptosis in epithelial lung cells we investigated glyoxal-dependent changes in pro- and antiapoptotic mediators bax and activated caspase-3, and galectin-3 and bcl-2, respectively. Increasing concentrations of glyoxal (50 to 400 microM) induced an increase in the number of apoptotic cells. The apoptotic changes were confirmed by transmission electron microscopy. Immunocytochemical analysis of treated cells revealed the presence of other AGEs such as pentosidine as well as products of lipid peroxidation.