Educators' consideration of learner motivation in ophthalmology education in medical school: Influences on teaching practice and course design

BACKGROUND

Ophthalmology education in medical school has historically neglected the impact of autonomous motivation on student learning and wellbeing. This study aimed to understand ophthalmology educators' consideration and application of student motivation in ophthalmology medical education.

MATERIAL AND METHODS

Lead ophthalmology educators from Australian and New Zealand medical schools participated in an online semi-structured in-depth interview. Interview transcripts were analysed using thematic analysis. Codes were generated and aligned into overarching themes.

FINDINGS

Six educators participated in the study. Five main themes arose from the transcripts: the lack of explicit consideration of student motivation, implicit consideration of motivation in curriculum design and in teaching practices, the impact of innovation on motivation and the relationship between teacher and student motivation. Participants also commented on trends in ophthalmology education including generalists' confidence in managing ophthalmic disease, the role of fundoscopy in medical education and time pressure on ophthalmology in medical schools.

CONCLUSION

There has only been an implicit instead of explicit consideration of motivation in ophthalmology education in medical school, which leaves an unfulfilled potential for teaching practices to impact the affective along with cognitive and metacognitive aspects of learning. This study highlights the need for motivation to be explicitly incorporated into the development of teaching practices and curriculum reform.

Long-term limitations and complications of trans-scleral diode laser cycloablation for refractory glaucoma

BACKGROUND

Trans-scleral diode laser cycloablation (cyclodiode) is effective in the short-term management of refractory glaucoma where alternative treatments are not feasible. Long-term outcomes of 5-years or more are not well-documented, particularly in relation to intraocular pressure (IOP) control, need for further procedures and complications such as hypotony and phthisis.

METHODS

A review was undertaken of patient medical records with refractory glaucoma who underwent cyclodiode at City Eye Centre in Brisbane from 2012 to 2016. Data included sex, age, laterality, type of glaucoma, cyclodiode parameters, number of glaucoma medications, visual acuity and treatment with acetazolamide. Data were analysed using generalised linear modelling and Kaplan-Meier analysis.

RESULTS

A total of 54 eyes in 54 patients (29 M:25F) with a mean age of 66 years (range 15-85 years) with a minimum of 5 years follow up were included. The mean number of burns was 23.3 (range 12-40) over 180-270 degrees, mean power per burn was 1967 mW (range 1500-2000 mW), with a mean duration of 1981 ms (1500-2000 ms). The mean pre-treatment IOP was 31.5 mmHg (range 17-56 mmHg) and mean IOP 5 years post-treatment was 16.1 mmHg (2-42 mmHg). The mean number of pre-treatment medications was 3.6 (range 1-6) and 2.7 (range 0-5) 5 years post treatment, including 5 (8.3%) on oral acetazolamide. Complications of cyclodiode were seen in 6 (11.1%) patients, including 3 (5.0%) cases of hypotony, and 2 (3.3%) phthisis.

CONCLUSION

Cyclodiode is often utilised for end-stage glaucoma when the IOP is uncontrolled on medical treatment and drainage surgery is not indicated, resulting in long-term reduction of IOP and the number of medications, including acetazolamide. Hypotony and phthisis can be significant complications.

Ophthalmology teaching in Australian medical schools: A national survey

PURPOSE

To survey the current educational trends and methods of ophthalmology teaching in Australian undergraduate and postgraduate medical schools.

MATERIALS AND METHODS

Cross-sectional survey; National online survey distributed to Australian university undergraduate and post-graduate medical schools from November 2020 to March 2021. The survey encompassed 35 questions on student demographics, teaching methods, core theoretical topics, clinical skills, and assessment methods in ophthalmology. One survey per institution completed by the relevant individual responsible for curriculum.

RESULTS

Total response rate of 90.48% (19 of 21 medical schools) was received with good representation across Australia. Ophthalmology rotations were required in 63.3% (n = 12), while 36.7% (n = 7) did not have mandatory terms. This compares favourably to the USA (16%), Canada (35.7%) and equivalent to UK (65%). 74% (n = 14) state ophthalmology is not a priority in the curriculum. All respondents reported student exposure to at least one clinical day in ophthalmology, with total teaching time ranging from less than six hours (36.9%), up to greater than two weeks (10.5%). Overall, only 31.6% reported utilisation of the International Council of Ophthalmology (ICO) curriculum in curricular development.

CONCLUSIONS

Ophthalmology medical school teaching in Australia remains reasonable when compared internationally, but there is significant variation amongst universities. Incorporation of the ICO curriculum and development of shared resources would enhance medical graduates' competence.

Brain Α-Tocopherol Concentration is Inversely Associated with Neurofibrillary Tangle Counts in Brain Regions Affected in Earlier Braak Stages: A Cross-Sectional Finding in the Oldest Old

Objectives

Higher vitamin E status has been associated with lower risk of Alzheimer's disease (AD). However, evidence of the association of vitamin E concentration in neural tissue with AD pathologies is limited.

Design

The cross-sectional relationship between the human brain concentrations of α- and γ-tocopherol and the severity of AD pathologies - neurofibrillary tangle (NFT) and neuritic plaque (NP) - was investigated.

Setting & Participants

Brains from 43 centenarians (≥ 98 years at death) enrolled in the Phase III of the Georgia Centenarian Study were collected at autopsy.

Measurements

Brain α- and γ-tocopherol concentrations (previously reported) were averaged from frontal, temporal, and occipital cortices. NP and NFT counts (previously reported) were assessed in frontal, temporal, parietal, entorhinal cortices, amygdala, hippocampus, and subiculum. NFT topological progression was assessed using Braak staging. Multiple linear regression was performed to assess the relationship between tocopherol concentrations and NP or NFT counts, with and without adjustment for covariates.

Results

Brain α-tocopherol concentrations were inversely associated with NFT but not NP counts in amygdala (β = -2.67, 95% CI [-4.57, -0.79]), entorhinal cortex (β = -2.01, 95% CI [-3.72, -0.30]), hippocampus (β = -2.23, 95% CI [-3.82, -0.64]), and subiculum (β = -2.52, 95% CI [-4.42, -0.62]) where NFT present earlier in its topological progression, but not in neocortices. Subjects with Braak III-IV had lower α-tocopherol (median = 69,622 pmol/g, IQR = 54,389-72,155 pmol/g) than those with Braak I-II (median = 72,108 pmol/g, IQR = 64,056-82,430 pmol/g), but the difference was of borderline significance (p = 0.063). γ-Tocopherol concentrations were not associated with either NFT or NP counts in any brain regions assessed.

Conclusions

Higher brain α-tocopherol level is specifically associated with lower NFT counts in brain structures affected in earlier Braak stages. Our findings emphasize the possible importance of α-tocopherol intervention timing in tauopathy progression and warrant future clinical trials.

B-Vitamin Therapy for Kidney Transplant Recipients Lowers Homocysteine and Improves Selective Cognitive Outcomes in the Randomized FAVORIT Ancillary Cognitive Trial

BACKGROUND

Objectives: Elevated plasma total homocysteine (tHcy) is associated with increased risk of cardiovascular disease, stroke and dementia. Results of clinical trials using B-vitamins to reduce the cognitive risks attributed to tHcy have been inconsistent. The high prevalence of both hyperhomocysteinemia and cognitive impairment among kidney transplant recipients makes them an important population in which to evaluate the effect of lowering homocysteine on cognitive function. We therefore evaluated whether B-vitamin therapy to lower tHcy would prevent cognitive-decline in a cohort of stable kidney transplant recipients.

DESIGN

The study was a longitudinal ancillary of the FAVORIT trial, a randomized, placebo-controlled multi-site trial of high-dose B vitamins to reduce cardiovascular and cerebrovascular events in clinically stable kidney transplant recipients with elevated tHcy.

PARTICIPANTS

584 participants from 18 sites across North America.

INTERVENTION

The intervention consisted of a daily multivitamin containing high-doses of folate (5.0 mg), vitamin B12 (1.0 mg) and vitamin B6 (50 mg). The placebo consisted of a daily multi-vitamin containing no folate and recommended daily allowances of vitamins B12 and B6 (0 mg folate; 2.0 µg vitamin B12; 1.4 mg vitamin B6).

MEASUREMENTS

Annual neuropsychological assessment for up to 5 years (mean 3.3 years) using a standardized test battery. Efficacy was analyzed on an intention-to-treat basis using end-of-trial data. Subgroup analyses included stratification for baseline plasma B-vitamin and tHcy concentrations.

RESULTS

At baseline, cognitive impairment was common with 61% of participants falling more than one standard deviation below published norms for at least one cognitive test. Fewer than 1% of participants had insufficient plasma folate < 5 ng/ml or vitamin B12 < 148 pmol/L. However, 44.6% had plasma B6 concentrations < 30 nmol/L. At follow-up, processing speed and memory scores were modestly but significantly better in the B-vitamin supplement group than in controls (p≤0.05). There was no interaction between baseline tHcy, B-vitamin status and treatment on the cognitive outcomes.

CONCLUSIONS

High-dose B-vitamin supplementation provided modest cognitive benefit for kidney transplant recipients with elevated baseline tHcy. Since nearly all participants were folate and vitamin B12 sufficient at baseline, the potential cognitive benefits of folate and B12 supplementation in individuals with poor B-vitamin status remains to be determined.

Indicator microbes correlate with pathogenic bacteria, yeasts and helminthes in sand at a subtropical recreational beach site

AIMS

Research into the relationship between pathogens, faecal indicator microbes and environmental factors in beach sand has been limited, yet vital to the understanding of the microbial relationship between sand and the water column and to the improvement of criteria for better human health protection at beaches. The objectives of this study were to evaluate the presence and distribution of pathogens in various zones of beach sand (subtidal, intertidal and supratidal) and to assess their relationship with environmental parameters and indicator microbes at a non-point source subtropical marine beach.

METHODS AND RESULTS

In this exploratory study in subtropical Miami (Florida, USA), beach sand samples were collected and analysed over the course of 6 days for several pathogens, microbial source tracking markers and indicator microbes. An inverse correlation between moisture content and most indicator microbes was found. Significant associations were identified between some indicator microbes and pathogens (such as nematode larvae and yeasts in the genus Candida), which are from classes of microbes that are rarely evaluated in the context of recreational beach use.

CONCLUSIONS

Results indicate that indicator microbes may predict the presence of some of the pathogens, in particular helminthes, yeasts and the bacterial pathogen Staphylococcus aureus including methicillin-resistant forms. Indicator microbes may thus be useful for monitoring beach sand and water quality at non-point source beaches.

SIGNIFICANCE AND IMPACT OF THE STUDY

The presence of both indicator microbes and pathogens in beach sand provides one possible explanation for human health effects reported at non-point sources beaches.

25-Hydroxyvitamin D, dementia, and cerebrovascular pathology in elders receiving home services

BACKGROUND

Vitamin D deficiency has potential adverse effects on neurocognitive health and subcortical function. However, no studies have examined the association between vitamin D status, dementia, and cranial MRI indicators of cerebrovascular disease (CVD).

METHODS

Cross-sectional investigation of 25-hydroxyvitamin D [25(OH)D], dementia, and MRI measures of CVD in elders receiving home care (aged 65-99 years) from 2003 to 2007.

RESULTS

Among 318 participants, the mean age was 73.5 +/- 8.1 years, 231 (72.6%) were women, and 109 (34.3%) were black. 25(OH)D concentrations were deficient (<10 ng/mL) in 14.5% and insufficient (10-20 ng/mL) in 44.3% of participants. There were 76 participants (23.9%) with dementia, 41 of which were classified as probable AD. Mean 25(OH)D concentrations were lower in subjects with dementia (16.8 vs 20.0 ng/mL, p < 0.01). There was a higher prevalence of dementia among participants with 25(OH)D insufficiency (< or =20 ng/mL) (30.5% vs 14.5%, p < 0.01). 25(OH)D deficiency was associated with increased white matter hyperintensity volume (4.9 vs 2.9 mL, p < 0.01), grade (3.0 vs 2.2, p = 0.04), and prevalence of large vessel infarcts (10.1% vs 6.9%, p < 0.01). After adjustment for age, race, sex, body mass index, and education, 25(OH)D insufficiency (< or =20 ng/mL) was associated with more than twice the odds of all-cause dementia (odds ratio [OR] = 2.3, 95% confidence interval [CI] 1.2-4.2), Alzheimer disease (OR = 2.5, 95% CI 1.1-6.1), and stroke (with and without dementia symptoms) (OR = 2.0, 95% CI 1.0-4.0).

CONCLUSIONS

Vitamin D insufficiency and deficiency was associated with all-cause dementia, Alzheimer disease, stroke (with and without dementia symptoms), and MRI indicators of cerebrovascular disease. These findings suggest a potential vasculoprotective role of vitamin D.

Simultaneous concentration of Enterococci and coliphage from marine waters using a dual layer filtration system

Concentrating diverse microbes in a time and cost effective manner is an essential component in water quality monitoring of recreational beaches. Historically, detection of bacteria and viruses requires two different capture methods to detect both types of organisms in a given water sample. The purpose of this present study was to evaluate a newly devised dual layered filtration system, which was developed to simultaneously concentrate both viruses and bacteria in one step from marine waters. An apparatus was designed to accommodate two 90-mm diam., 0.45 microm pore size membranes in series, one on top of the other. The top polyvinylidene fluoride (PVDF) membrane was used to filter bacteria by physical straining while the bottom HA membrane retained viruses through adsorption. Results indicated that the dual layer filtration system recovered 83+/-14% of the test bacteria (Enterococcus fecalis) and 81+/-28% of the test virus (MS2 coliphage) on the top and bottom membranes, respectively. This research demonstrates the potential of using a dual layered filtration system for the simultaneous concentration of both bacteria and viruses on separate filters from recreational beach waters. This system is relatively simple to use, inexpensive, and has the potential to be suitable for routine monitoring. This study serves as a proof of concept for the technique. Additional experiments are needed to evaluate the system on a variety of different bacteria and viruses as well as on water with different physical and chemical parameters.

Confirmation of putative stormwater impact on water quality at a Florida beach by microbial source tracking methods and structure of indicator organism populations

The effect of a stormwater conveyance system on indicator bacteria levels at a Florida beach was assessed using microbial source tracking methods, and by investigating indicator bacteria population structure in water and sediments. During a rain event, regulatory standards for both fecal coliforms and Enterococcus spp. were exceeded, contrasting with significantly lower levels under dry conditions. Indicator bacteria levels were high in sediments under all conditions. The involvement of human sewage in the contamination was investigated using polymerase chain reaction (PCR) assays for the esp gene of Enterococcus faecium and for the conserved T antigen of human polyomaviruses, all of which were negative. BOX-PCR subtyping of Escherichia coli and Enterococcus showed higher population diversity during the rain event; and higher population similarity during dry conditions, suggesting that without fresh inputs, only a subset of the population survives the selective pressure of the secondary habitat. These data indicate that high indicator bacteria levels were attributable to a stormwater system that acted as a reservoir and conduit, flushing high levels of indicator bacteria to the beach during a rain event. Such environmental reservoirs of indicator bacteria further complicate the already questionable relationship between indicator organisms and human pathogens, and call for a better understanding of the ecology, fate and persistence of indicator bacteria.

Multivitamin use and B vitamin status in a homebound elderly population

OBJECTIVE

Homebound elderly are at increased risk for micronutrient deficiencies and nutritional status in this population has not been adequately described. There is evidence for beneficial effects of multivitamin use and a greater understanding of their nutritional contribution could identify behaviors that may help alleviate excess chronic disease. The purpose of this analysis is to investigate, in a racially diverse group of homebound elders, the association of multivitamin use with measures of plasma B vitamin concentrations.

DESIGN

We examined the cross-sectional association between multivitamin use and plasma concentrations of B vitamins and homocysteine in 236 white and 182 black homebound elders (65-99y). Dietary intake was assessed and demographic and health information was ascertained.

RESULTS

White and black elders had a high prevalence of dietary intakes below the Estimated Average Requirement for folate (38.1 and 40.7%), vitamin B6 (16.9 and 19.2%.), and vitamin B12 (3 and 3.9%) respectively. Multivitamin use was associated with higher mean plasma B vitamin concentrations in each group. In whites, multivitamin users had higher concentrations of vitamin B6 (64.6 vs. 32.4 nmol/L; p < 0.001), vitamin B12 (398 vs. 324 pmol/L;p < 0.001) and folate (39.4 vs. 30.4 nmol/L;p < 0.001). Black multivitamin users had higher concentrations of vitamin B6 (53.7 vs. 29.5 nmol/L; p < 0.001), B12 (427 vs. 372 pmol/L; p < 0.05) and folate (35.7 vs. 25.4 nmol/L; < 0.001) than non-users.

CONCLUSIONS

Multivitamin supplementation was associated with higher mean plasma concentrations of vitamins B6, B12, and folate and lower prevalence of low plasma B vitamin status in a biracial homebound elderly.

Geographical variation in antibiotic resistance profiles of Escherichia coli isolated from swine, poultry, beef and dairy cattle farm water retention ponds in Florida1

AIMS

The aim of this study was to assess geographical variation in multiple antibiotic resistance (MAR) profiles of livestock Escherichia coli as well as to evaluate the ability of MAR profiles to differentiate sources of faecal pollution.

METHODS AND RESULTS

More than 2000 E. coli isolates were collected from water retention ponds and manure of swine, poultry, beef and dairy farms in south, central and north Florida, and analysed for MAR using nine antibiotics. There were significant differences in antibiotic resistance of E. coli by season and livestock type for more than one antibiotic, but regional differences were significant only for ampicillin. Over the three regions, discriminant analysis using MAR profiles correctly classified 27% of swine, 49% of poultry, 56% of beef and 51% of dairy isolates.

CONCLUSIONS

Regional variations in MAR combined with moderate discrimination success suggest that MAR profiles of E. coli may only be marginally successful in identifying sources of faecal pollution.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study demonstrates the existence of regional and seasonal differences in MAR profiles as well as the limited ability of MAR profiles to discriminate among livestock sources.

Assessment of virulence-factor activity relationships (VFARs) for waterborne diseases

Virulence-factor activity relationship (VFAR) is a concept that was developed as a way to relate the architectural and biochemical components of a microorganism to its potential to cause human disease. Development of these relationships requires specialised bioinformatics databases that do not exist at present. A pilot-scale VFAR database was designed for three different waterborne organisms: Escherichia coli, Norovirus and Cryptosporidium, to evaluate VFAR relationships. For the web-based database, each organism has separate pages containing virulence genes, occurrence genes, primer sets and probes, taxonomy, outbreaks, and serotype/species/genogroup/genotype. As the database continues to grow, it will be possible to relate the occurrence and prevalence of certain genes in various microorganisms to outbreak data and, subsequently, to establish the utility of using a combination of specific genes as markers of virulence and in establishing virulence-factor activity relationships (VFARs). The database and the VFARs established will be of use to the regulatory community as a way to assist with prioritising those organisms, which need to be regulated.

Assessment of methods for detection of infectious Cryptosporidium oocysts and Giardia cysts in reclaimed effluents

This study evaluates the occurrence of Cryptosporidium oocysts and Giardia cysts in reclaimed effluents if method 1623 with the Envirochek capsule filters (standard and high-volume [HV] filters) and a modified version of the Information Collection Rule method (ICR) with the polypropylene yarn-wound cartridge filter are used. The recovery efficiency of the analytical methods was evaluated with samples of reagent, tap, and reclaimed water by using flow cytometer-sorted spike suspensions. (Oo)cyst recovery efficiency determined filter performance and method reproducibility in the water matrix tested. Method 1623 with the Envirochek HV capsule filter generated significantly higher recovery rates than did the standard Envirochek filter and the modified ICR method. Notwithstanding, large variations in recovery rates (>80%) occurred with samples of reclaimed water, and none of the water quality parameters analyzed in the reclaimed effluents could explain such variability. The highest concentrations of indigenous oocysts were detected by method 1623 with the HV filter, which provided a sufficient number of oocysts for further confirmation of infectious potential. Confirmation of species and potential infectivity for all positive protozoan samples was made by using a nested PCR restriction fragment polymorphism assay and the focus detection method most-probable-number assay, respectively. The methodology and results described in the present investigation provide useful information for the establishment of pathogen numeric standards for reclaimed effluents used for unrestricted irrigation.

Elution, detection, and quantification of polio I, bacteriophages, Salmonella montevideo, and Escherichia coli O157:H7 from seeded strawberries and tomatoes

This study compared the effect of different physical and chemical treatments of strawberries and tomatoes to determine their ability to recover seeded viral and bacterial pathogens from produce surfaces. Solutions of salts, amino acids, complex media, and detergents were compared as eluants. Phosphate-buffered saline (PBS) containing 0.1% Tween 80 eluted the highest number of seeded microorganisms. Elution with this defined solution was then compared under different conditions of physical agitation. Rotary shaking for 20 min at 36 degrees C eluted higher numbers of viruses and bacteria than did low- or high-speed stomaching. Commercially available and laboratory prepared bacteriological differential media were compared for their ability to recover and distinguish eluted Salmonella Montevideo and Escherichia coli O157:H7 strains from seeded produce. The recovery of seeded bacterial pathogens was low when differential media containing selective ingredients were used (MacConkey sorbitol agar, XLD agar, MacConkey agar). Highest recoveries were obtained on a medium consisting of tryptic soy agar supplemented with sodium thiosulfate and ferric ammonium citrate compared with selective media that inhibited up to 50% of the growth of the eluted microorganisms.

Influence of salts on virus adsorption to microporous filters

We investigated the direct and indirect effects of mono-, di-, and trivalent salts (NaCl, MgCl(2), and AlCl(3)) on the adsorption of several viruses (MS2, PRD-1, phiX174, and poliovirus 1) to microporous filters at different pH values. The filters studied included Millipore HA (nitrocellulose), Filterite (fiberglass), Whatman (cellulose), and 1MDS (charged-modified fiber) filters. Each of these filters except the Whatman cellulose filters has been used in virus removal and recovery procedures. The direct effects of added salts were considered to be the effects associated with the presence of the soluble salts. The indirect effects of the added salts were considered to be (i) changes in the pH values of solutions and (ii) the formation of insoluble precipitates that could adsorb viruses and be removed by filtration. When direct effects alone were considered, the salts used in this study promoted virus adsorption, interfered with virus adsorption, or had little or no effect on virus adsorption, depending on the filter, the virus, and the salt. Although we were able to confirm previous reports that the addition of aluminum chloride to water enhances virus adsorption to microporous filters, we found that the enhanced adsorption was associated with indirect effects rather than direct effects. The increase in viral adsorption observed when aluminum chloride was added to water was related to the decrease in the pH of the water. Similar results could be obtained by adding HCl. The increased adsorption of viruses in water at pH 7 following addition of aluminum chloride was probably due to flocculation of aluminum, since removal of flocs by filtration greatly reduced the enhancement observed. The only direct effect of aluminum chloride on virus adsorption that we observed was interference with adsorption to microporous filters. Under conditions under which hydrophobic interactions were minimal, aluminum chloride interfered with virus adsorption to Millipore, Filterite, and 1MDS filters. In most cases, less than 10% of the viruses adsorbed to filters in the presence of a multivalent salt and a compound that interfered with hydrophobic interactions (0.1% Tween 80 or 4 M urea).

Vascular innervation in atherogenesis

Although collar-induced atherosclerosis continues to be used as an investigative tool, the underlying mechanism has not been established. Two primary mechanisms suggested are adventitial ischemia due to reduction in vasa vasorum, and perivascular denervation. We have examined the effect of injuring the common carotid artery in the pattern produced by the ends of a silastic collar, and have correlated the effect on innervation with change in intima/media ratios in normal and cholesterol-fed rabbits. The serum cholesterol of cholesterol-fed rabbits was significantly elevated by 10 days following initiation of cholesterol feeding, and further elevated at 21 days. No structural difference was detected between the uninjured carotid arteries of control and cholesterol-fed rabbits. At the site of injury in freeze injured carotid arteries there was a thickening of the intima which was increased in cholesterol-fed rabbits. The intima at the site of injury was composed of lipid-laden cells embedded in a matrix of collagen and elastin fibres. In carotid artery segments, between two sites of freeze injury, denervation was established by immunohistochemistry and electron microscopy. The denervated segments were not morphologically different from uninjured carotid arteries in either control or cholesterol-fed rabbits. While injury induced intimal thickening and foam cell development, denervation did not. It is concluded that perivascular denervation is a consequence of silastic collar application and is not involved in the induction of atherosclerosis.

Dynamic susceptibility contrast MR imaging of regional cerebral blood volume in Alzheimer disease: a promising alternative to nuclear medicine

BACKGROUND AND PURPOSE

The goal of our study was to evaluate the sensitivity and specificity for Alzheimer disease of semiquantitative dynamic susceptibility contrast (DSC) MR imaging as compared with results of qualitative single-photon emission computed tomography (SPECT) in the same patients and with previously published semiquantitative SPECT results.

METHODS

Fifty subjects were studied: 19 patients with probable Alzheimer disease with moderate cognitive impairment, eight mildly impaired patients with possible or probable Alzheimer disease, 18 group-matched elderly healthy comparison subjects, and five elderly comparison patients with psychiatric diagnoses. Relative values of temporoparietal regional cerebral blood volume (rCBV) were measured as a percentage of cerebellar rCBV, and group classification was assessed with logistic regression. The DSC MR imaging results were compared with SPECT scans in these same subjects and with previously published semiquantitative SPECT data.

RESULTS

Temporoparietal rCBV ratios were reduced 20% bilaterally in the patients with Alzheimer disease. Using left and right temporoparietal rCBV as index measures, sensitivity was 95% in moderately affected patients with Alzheimer disease and 88% in patients with mild cases. Specificity was 96% in healthy comparison subjects and in psychiatric comparison subjects. Sensitivity with DSC MR imaging was considerably better than with visual clinical readings of SPECT scans (74% in moderate and 50% in mild Alzheimer disease cases), and was similar to previous published SPECT temporoparietal measurements (90%). Specificity with SPECT was 100% visually and 87% based on previous temporoparietal measurements.

CONCLUSIONS

DSC MR imaging of rCBV is promising as a safe, potentially lower-cost alternative to nuclear medicine imaging for the evaluation of patients with dementia.

Isolation of an amoeba naturally harboring a distinctive Legionella species

There are numerous in vitro studies documenting the multiplication of Legionella species in free-living amoebae and other protozoa. It is believed that protozoa serve as host cells for the intracellular replication of certain Legionella species in a variety of environmental settings. This study describes the isolation and characterization of a bacterium initially observed within an amoeba taken from a soil sample. In the laboratory, the bacterium multiplied within and was highly pathogenic for Acanthamoeba polyphaga. Extracellular multiplication was observed on buffered charcoal yeast extract agar but not on a variety of conventional laboratory media. A 16S rRNA gene analysis placed the bacterium within the genus Legionella. Serological studies indicate that it is distinct from previously described species of the genus. This report also describes methods that should prove useful for the isolation and characterization of additional Legionella-like bacteria from free-living amoebae. In addition, the characterization of bacterial pathogens of amoebae has significant implications for understanding the ecology and identification of other unrecognized bacterial pathogens.

Dynamic susceptibility contrast MRI of regional cerebral blood volume in Alzheimer's disease

OBJECTIVE

The purpose of this study was to investigate the potential effectiveness of dynamic susceptibility contrast magnetic resonance imaging (MRI) to discriminate elderly patients with Alzheimer's disease from normal matched comparison subjects.

METHOD

Images of regional cerebral blood volume (CBV) were generated from echo-planar MRI with the dynamic susceptibility contrast method in 13 Alzheimer's disease patients and 13 comparison subjects group-matched on age and gender.

RESULTS

Temporoparietal cerebral blood volume, expressed as a percentage of the cerebellum value, was reduced 17% bilaterally in the patients with Alzheimer's disease. Blood volume in sensorimotor regions was reduced only 8.5% in the patients. Discriminant function analysis based on left and right temporoparietal measures correctly classified 88.5% of the subjects as patients or comparison subjects. Temporoparietal CBV was reduced even in mildly affected Alzheimer's disease patients (Mini-Mental State scores > 24).

CONCLUSIONS

Dynamic susceptibility contrast MRI of regional CBV is promising as a nonradioactive, potentially lower-cost alternative to other functional neuroimaging methods for evaluating Alzheimer's disease.

Severe cardiovascular disease and Alzheimer's disease: senile plaque formation in cortical areas

The main objectives of this study were to analyze the distribution of senile plaques (SP) and neurofibrillary tangles (NFT) in different cortical areas of patients suffering from severe cardiovascular diseases (CVD) and to compare them with Alzheimer's disease (AD) cases. Forty brains were divided into three groups: an AD group (n = 12), a CVD group (n = 17), and a nonheart disease control group (n = 11). The cortical areas examined were the middle frontal gyrus, the superior and inferior watershed areas, the hippocampal formation with the transentorhinal cortex, and the primary visual cortex. SP and NFT were counted in Bielschowsky-stained sections from all cortical areas and from the hippocampal formation and the transentorhinal cortex, respectively. Patients with severe CVD occupied an intermediate position in the spectrum of SP formation between AD and nonheart disease patients. The CVD group showed a higher prevalence of SP than the control group, and SP counts were significantly larger in the inferior watershed area, dentate gyrus, subiculum, and transentorhinal cortex. The distribution of SP was similar in CVD and AD patients. Control and CVD patients showed no difference regarding the number of NFT. The existence of a possible cardiovascular component in the genesis of SP is discussed.

Deficits in short-term memory in adult survivors of childhood abuse

Exposure to stress has been associated with alterations in memory function, and we have previously shown deficits in short-term verbal memory in patients with a history of exposure to the stress of combat and the diagnosis of posttraumatic stress disorder (PTSD). Few studies of any kind have focused on adult survivors of childhood physical and sexual abuse. The purpose of this study was to investigate short-term memory function in adult survivors of childhood abuse. Adult survivors of severe childhood physical and sexual abuse (n = 21), as defined by specific criteria derived from the Early Trauma Inventory (ETI), who were presenting for psychiatric treatment were compared with healthy subjects (n = 20) matched for several variables including age, alcohol abuse, and years of education. All subjects were assessed with the Wechsler Memory Scale (WMS) Logical (verbal memory) and Figural (visual memory) components, the Verbal and Visual Selective Reminding Tests (SRT), and the Wechsler Adult Intelligence Scale-Revised (WAIS-R). Adult survivors of childhood abuse had significantly lower scores on the WMS Logical component for immediate and delayed recall in comparison to normal subjects, with no difference in visual memory, as measured by the WMS or the SRT, or IQ, as measured by the WAIS-R. Deficits in verbal memory, as measured by the WMS, were associated with the severity of abuse, as measured by a composite score on the ETI. Our findings suggest that childhood physical and sexual abuse is associated with long-term deficits in verbal short-term memory. These findings of specific deficits in verbal (and not visual) memory, with no change in IQ, are similar to the pattern of deficits that we have previously found in patients with combat-related PTSD.

Effect of denervation of the rat superior mesenteric arterial bed on the distribution of resistance among the first four orders of branching

The rat superior mesenteric artery with its first four orders of branching has been examined as an isolated perfused preparation. Lumen diameter and proportional resistance at each level have been determined and compared under conditions of constant pressure following methoxamine-induced constriction and acetylcholine-induced relaxation in intact and denervated preparations. A comparison was also made between intact preparations under conditions of constant pressure and constant flow. Lumen diameter and segment length were measured by analysis of video-taped images. The distribution of resistance among the first four orders of branching was estimated from the measured values using the Poiseuille formula. Intact first and fourth order branches had a proportionately low resistance, with the remaining resistance being fairly evenly distributed between the second and third order branches. No change in the pattern occurred as a result of either methoxamine or acetylcholine treatment. The pattern of distribution of resistance changed following denervation, so that proportional resistance was high in the first order branches and fell off from the second to fourth order branches. With methoxamine, the first order branches of denervates had a significantly higher resistance than in intact tissues, with the distribution of resistance in the second to fourth order branches following the basal resistance pattern. Reduction in the proportion of resistance with acetylcholine was similar in both intact and denervated preparations. Distribution of resistance did not differ between constant flow and constant pressure intact preparations.

MRI-based measurement of hippocampal volume in patients with combat-related posttraumatic stress disorder

OBJECTIVE

Studies in nonhuman primates suggest that high levels of cortisol associated with stress have neurotoxic effects on the hippocampus, a brain structure involved in memory. The authors previously showed that patients with combat-related posttraumatic stress disorder (PTSD) had deficits in short-term memory. The purpose of this study was to compare the hippocampal volume of patients with PTSD to that of subjects without psychiatric disorder.

METHOD

Magnetic resonance imaging was used to measure the volume of the hippocampus in 26 Vietnam combat veterans with PTSD and 22 comparison subjects selected to be similar to the patients in age, sex, race, years of education, socioeconomic status, body size, and years of alcohol abuse.

RESULTS

The PTSD patients had a statistically significant 8% smaller right hippocampal volume relative to that of the comparison subjects, but there was no difference in the volume of other brain regions (caudate and temporal lobe). Deficits in short-term verbal memory as measured with the Wechsler Memory Scale were associated with smaller right hippocampal volume in the PTSD patients only.

CONCLUSIONS

These findings are consistent with a smaller right hippocampal volume in PTSD that is associated with functional deficits in verbal memory.

A case-based anatomy course

A course is described in which the students give consideration to clinical cases as they review their current knowledge, and follow a set protocol which guided them in preparing their learning. The students are required to examine a case history, put down as key words either their first answer or the knowledge they consider they would need to answer specific questions. They then select stations at which additional information, wet specimens, models and radiological images assist them in upgrading their knowledge. They complete the exercise by writing a final answer to the questions on the case. The tutor is able through examination of the key words to determine the knowledge of the students as they enter, and confirm appropriate learning by inspection of the final answer. The students are able to identify their own deficiencies, develop strategies for thinking and learning, resulting in the acquisition of expertise in problem solving, and extend their communication skills by working with colleagues. While the course was designed for second-year anatomy teaching it could be applied to other disciplines.

Deficits in short-term memory in posttraumatic stress disorder

OBJECTIVE

The purpose of this study was to compare the memory function of patients with posttraumatic stress disorder (PTSD) to that of matched comparison subjects.

METHOD

Vietnam veterans with combat-related PTSD (N = 26) were compared to physically healthy comparison subjects (N = 15) matched for age, race, sex, years of education, handedness, socioeconomic status, and alcohol abuse. Memory and intelligence were assessed with a battery of neuropsychological tests, including the Russell revision of the Wechsler Memory Scale, the Selective Reminding Test, and subtests of the Wechsler Adult Intelligence Scale-Revised (WAIS-R).

RESULTS

The PTSD patients scored significantly lower than the comparison subjects on the Wechsler Memory Scale logical memory measures for immediate recall (mean = 11.6, SD = 3.3 versus mean = 20.9, SD = 6.6) and delayed recall (mean = 8.0, SD = 3.3 versus mean = 17.8, SD = 6.4). The PTSD patients also scored significantly lower on the total recall, long-term storage, long-term retrieval, and delayed recall measures for the verbal component of the Selective Reminding Test and on the recall, long-term storage, long-term retrieval, and continuous long-term retrieval measures for the visual component of the Selective Reminding Test. There was no significant difference between the PTSD patients and comparison subjects in prorated full-scale IQ as measured by the WAIS-R.

CONCLUSIONS

Patients with PTSD may have deficits in short-term memory. Counseling and rehabilitation that address these deficits may be of value for PTSD patients.

How we teach anatomy efficiently and effectively

An anatomy course is presented which stresses the teaching of applied anatomy using lectures, laboratory workshops and problem-solving tutorials. Laboratory workshops include the use of prosected specimens and body imaging such as CT scan and ultrasound, but do not include dissection. The problem-solving tutorials make extensive use of clinical cases and the application of anatomical knowledge. The course is taught by anatomists and practising physicians, and needs only 98 hours of curriculum time. The performance of the students and the positive attitudes of both students and faculty are enhanced by the design of the course.

Perivascular innervation is lost in experimental atherosclerosis

Nerve fibers, immunohistochemically positive for neuropeptide Y, tyrosine hydroxylase, calcitonin gene-related peptide and substance P, form a perivascular network surrounding the carotid arteries of New Zealand White rabbits. Transmission electron microscopy demonstrates that the nerve fibers are primarily located at the adventitial-medial border. Placing a silastic collar around a carotid artery for 14 days, in rabbits fed a diet high in cholesterol, resulted in a focal, intimal thickening in 10 out of 12 rabbits. Contralateral sham-operated arteries showed no intimal thickening. At sites where intimal thickening occurred, there was a disappearance of the perivascular nerve network. The carotid arteries from rabbits that did not respond to the collar and the sham-operated carotid arteries showed an intact and normal perivascular nerve network. In the group of animals which responded to the collar with intimal thickening, there was evidence of a proliferative response proximal to the collar and in this same tissue there was evidence of degeneration of nerve fibers. In conclusion, it has been demonstrated for the first time that, in regions of the carotid artery where intimal thickening occurred, there was an associated degeneration of the perivascular nerve network. The cause of this degeneration and its functional consequences require further investigation.

Quantitative magnetic resonance imaging in temporal lobe epilepsy: relationship to neuropathology and neuropsychological function

Magnetic resonance images (MRIs) were obtained from 25 patients with medically refractory epilepsy of temporal lobe origin (12 on the left, 13 on the right) and 14 right-handed control subjects. The hippocampi and temporal lobes were traced by computer on successive coronal images and the resulting measurements of area were summed for each region. The left and right hippocampi were symmetrical in the control subjects; however, for patients the hippocampus was smaller on the side of the seizure focus. Moreover, the left-right hippocampal ratio significantly differentiated the control subjects from each patient group. The left temporal lobe was significantly smaller than the right in control subjects. The epileptics' temporal lobes were smaller on the side of the seizure focus, compared to the temporal lobes in the control subjects. MRI hippocampal measurements were compared to hippocampal neuronal densities obtained postoperatively. Significant correlations were obtained between the ratio (side ipsilateral to focus/side contralateral to focus) of MRI hippocampal measurements and neuronal densities in all hippocampal subfields except CA2. Prior to surgery, patients were administered the Wechsler Memory Scale and the verbal Selective Reminding Test. Significant correlations existed between MRI measurements of the left hippocampus and the Wechsler logical memory percent retention scores and between the left temporal lobe measurements and the verbal Selective Reminding Test scores for patients with seizure foci in the left temporal lobe.

Capsaicin-sensitive nerves influence the release of atrial natriuretic factor by atrial stretch in the rat

Although many factors may modulate the release of atrial natriuretic factor (ANF), the primary mechanism has been demonstrated to be atrial stretch. Recent studies have led to the suggestion that the peptidergic innervation of the heart, through the release of peptides, may be involved in the control of ANF secretion. We have examined the influence of chronic capsaicin treatment on three models of atrial stretch that release ANF. This treatment inhibited ANF released through in vivo blood volume expansion and through balloon inflation in the right atrium of in vitro isolated perfused hearts. Immunohistochemical and electron microscopical analysis confirmed the absence of innervation of the heart by calcitonin gene related peptide and substance P immunoreactive nerve fibres and apparent lack of effect on atrial granules in capsaicin treated rats. We conclude that capsaicin-sensitive cardiac innervation is a component modulating the release of ANF, stimulated by atrial stretch in the rat.

Interrelationships of heterozygosity, growth rate and heterozygote deficiencies in the coot clam, Mulinia lateralis

Allozyme surveys of marine invertebrates commonly report heterozygote deficiencies, a correlation between multiple locus heterozygosity and size, or both. Hypotheses advanced to account for these phenomena include inbreeding, null alleles, selection, spatial or temporal Wahlund effects, aneuploidy and molecular imprinting. Previous studies have been unable to clearly distinguish among these alternative hypotheses. This report analyzes a large data set (1906 individuals, 15 allozyme loci) from a single field collection of the coot clam Mulinia lateralis and demonstrates (1) significant heterozygote deficiencies at 13 of 15 loci, (2) a correlation between the magnitude of heterozygote deficiency at a locus and the effect of heterozygosity at that locus on shell length, and (3) a distribution of multilocus heterozygosity which deviates from that predicted by observed single-locus heterozygosities. A critical examination of the abovementioned hypotheses as sources of these findings rules out inbreeding, null alleles, aneuploidy, population mixing and imprinting as sole causes. The pooling of larval subpopulations subjected to varying degrees of selection, aneuploidy or imprinting could account for the patterns observed in this study.

The relationship between innervation and arterial structure in late prenatal and early postnatal development of the rat jejunal artery

The peripheral nervous system exerts a trophic influence on target tissues. We have examined the development of the perivascular innervation of the rat jejunal artery and correlated the simultaneous development of the endothelium and medial smooth muscle. Before birth a close relationship exists between endothelial cells and the first layer of differentiating medial smooth muscle, whereas the nerve fibres at this stage are formed into large remote bundles. After birth the differentiation of the media continues and the endothelial cells become separated from the smooth muscle by a thick internal elastic lamina. The nerve fibres grow from the large peripheral bundles to reach the smooth muscle as small bundles or individual fibres, with those immunoreactive to anti-calcitonin gene-related peptide being best developed by birth. From these studies it would seem that it is unlikely that perivascular nerve fibres influence the early development of the arterial wall, but they suggest that endothelial cells are more likely to be involved.

Antenatal diagnosis of cephalothoracopagus twins in a triplet pregnancy. A case report

The occurrence of conjoined twins in a triplet pregnancy is rare. Cephalothoracopagus twins were diagnosed on ultrasonography at 17 weeks' gestation. This is the first case of conjoined twins in a triplet pregnancy diagnosed early enough antenatally to allow vaginal pregnancy termination.

The peptidergic innervation of the developing mesenteric vascular bed in the rat

We have followed the development of perivascular nerve fibres using antisera to substance P, calcitonin gene related peptide, neuropeptide Y and vasoactive intestinal polypeptide in the mesenteric vascular bed of developing Sprague-Dawley rats. The pattern and density of innervation appeared to be determined by one week of age. The pattern of innervation by SP- and CGRP-positive fibres was similar. The pattern of innervation by neuropeptide Y-containing fibres was distinct from that of SP and CGRP. The VIP-positive fibre plexus was sparse and irregular compared with the others examined. The density of innervation by all fibre types was highest in the jejunal arteries.

The differential contribution by individual enzymes of glycolysis and protein catabolism to the relationship between heterozygosity and growth rate in the coot clam, Mulinia lateralis

The locus-specific effects of heterozygosity upon individual growth rate were determined for 15 polymorphic enzymes among 1906 individuals from a single cohort sample of the marine bivalve Mulinia lateralis. Two measures of individual growth rate (total wet weight and shell length) were made at collection and after a period of growth in the laboratory. The correlation between heterozygosity and growth rate was independently determined for each locus using multiple linear regression, thereby providing a rank of individual locus effects; these differed significantly. The four estimated rankings of relative locus effects (initial length, initial weight, length added in the laboratory, and added weight) were not statistically different. That is, a locus with a large effect of heterozygosity on growth rate in nature had a similarly large effect on laboratory growth rate. The effect of a locus was not related to heterozygosity per se; some highly heterozygous loci had no detectable correlation with growth rate. The data contained two pairs of relatively tightly linked loci; in both cases one locus of a pair had significant effects on growth rate, while the other had no effect. Loci with large and significant correlations with growth rate synthesize enzymes which function in protein catabolism or glycolysis; heterozygosity in enzymes of the pentose shunt, redox balance, or other miscellaneous metabolic roles was not correlated with growth rate. Since the metabolic basis for the correlation is known to derive from individual differences in net energy status, particularly energetic costs of whole-body protein turnover, these data indicate that phenotypic effects (e.g., variation in growth rate) are determined by heterozygosity at the studied genes, not other linked loci.

Apolipoprotein B allotypes MB19(1) and MB19(2) in subjects with coronary artery disease and hypercholesterolemia

We recently characterized a common form of genetic polymorphism in human apolipoprotein (apo) B, using the specific monoclonal antibody MB19 (Young SG, et al. Proc Natl Acad Sci USA 1986; 83:1101-1105). Antibody MB19 binds apo B with one of three distinct patterns of immunoreactivity (strong, intermediate, or weak). These three binding patterns are the result of the codominant inheritance of two common apo B alleles which encode for apo B allotypes MB19(1) and MB19(2), which have high and low affinity, respectively, for antibody MB19. Thus, subjects with strong or weak binding patterns are homozygous for MB19(1) or MB19(2), respectively, whereas those with an intermediate pattern are heterozygotes. To assess whether the MB19 polymorphism was related to hypercholesterolemia (HC) or to coronary artery disease (CAD), we determined the MB19 binding pattern and plasma lipoprotein concentrations in 129 normal subjects, 51 patients with HC, and 149 patients with CAD. The percentages of normal subjects having the strong, intermediate, and weak binding patterns were 11.6%, 41.9%, and 46.5%, respectively. The frequency of the three MB19 binding patterns was nearly the same in the groups with HC and CAD. Also, within each of the three groups of subjects, the MB19 binding pattern did not influence the plasma lipoprotein concentrations. We conclude that the genetic polymorphism in apo B defined by antibody MB19 is a common allelic variation in apo B, and that in the populations studied, it does not appear to be associated with the development of coronary artery disease or hypercholesterolemia.

Parallel expression of the MB19 genetic polymorphism in apoprotein B-100 and apoprotein B-48. Evidence that both apoproteins are products of the same gene

Immunochemical studies have demonstrated that apoprotein B-100 and apoprotein B-48 share some antigenic determinants, but whether they are products of the same gene has remained uncertain. Utilizing a specific mouse monoclonal antibody, MB19, we recently characterized a common form of genetic polymorphism that was expressed in apo-B-100 (Young, S. G., Bertics, S. J., Curtiss, L. K., Casal, D. C., and Witztum, J.L. (1985) Proc. Natl. Acad. Sci. U.S.A., in press). Antibody MB19 binds different allotypes of apo-B-100 (MB19(1) and MB19(2] with high and low affinities, respectively. Compared to a rabbit antiserum against human low density lipoprotein, which detects 100% of apo-B mass in all individuals, antibody MB19 detects 100% of apo-B with allotype MB19(1) but less than 10% of apo-B with allotype MB19(2). Western blots demonstrate that MB19 binds to both apo-B-100 and apo-B-48. To determine if apo-B-48 and apo-B-100 from the same individual express the same polymorphism, chylomicrons and very low density lipoproteins were isolated from 23 subjects in whom the allotypes of apo-B-100 were known. Delipidated apoproteins were separated electrophoretically and then transferred to nitrocellulose membranes. Nitrocellulose membranes were incubated with 125I-MB19 (to detect the polymorphism) and 131I-antiserum to human apo-B (to quantitate total apo-B transferred to nitrocellulose membranes). Apo-B-100 and apo-B-48 bands were removed and the ratio of 125/131 counts in each band was calculated. In all 23 subjects studied, the same MB19 polymorphism was present in both apo-B-100 and apo-B-48. This observation provides strong evidence that both apoproteins are products of the same gene.

Vascular and neural changes in the rat optic nerve following induction of diabetes with streptozotocin

This study was undertaken to determine whether or not changes occur in blood vessels, axons or glia of the optic nerve as the result of streptozotocin-induced diabetes. Diabetes was induced in 4 weeks old Sprague-Dawley rats. At 12 and 16 weeks of age, the rats were killed and the optic nerves prepared for examination. The number and density of blood vessels was found to be significantly increased in the diabetic rats. No alteration in the structure of the blood vessels was noted. A decrease in the percentage volume of axons and an increase in the percentage volume of glial elements accompanied the increase in blood vessels in the diabetic rats. No difference was found in the spectrum of fibre diameters.

An examination of the evidence for the existence of preformed pathways in the neural tube of Xenopus laevis

We have examined the neural tube in Xenopus laevis tadpoles to investigate the anatomical guidance elements which may be present in the presumptive marginal zone. With appropriate fixation protocols the neuroepithelial cells appeared in contact; electron microscopic observations failed to show any specialized intercellular spaces preceding the growing axons. The first fibres were found in the intercellular clefts between the neuroepithelial cells near the surface of the neural tube. Reconstructions of the neural tube from examination of serial 1 micron sections showed that the intercellular clefts are non-aligned at this stage and branching. Scanning electron microscopy of the surface of the neural tube confirmed that the intercellular spaces are non-aligned and often branch caudal to the growing front of descending axons. Thus to grow in a consistent direction the developing axons may have to make consistent and selective (specific) selections of pathway at numerous branch points if their growth is restricted to these intercellular clefts. As more axons grow along the neural tube, the intercellular clefts become wider, and the neuroepithelial cells bounding the clefts become indented. At later stages many fibres were observed with both scanning and transmission electron microscopy to grow along the surface of the neural tube. These changes in neuroepithelial cell morphology and fibre pathway allow axons to form bundles which take a fairly straight course in contrast to the winding path which must be taken by the first axons to grow through the intercellular clefts.

The relationship between altered blood vessel structure, hypertension, and the sympathetic nervous system

The relationship between sympathetic innervation and arterial medial development has been examined in normotensive, hypertensive, and diabetic rats. Using the jejunal artery as a model, the number of nerve fibres innervating the artery as determined from fluorescent preparations, and the medial thickness and lumen diameter as measured from resin embedded specimens were correlated from animals prepared in various ways. The rats used were normal Sprague-Dawley (SD), SD with induced hypertension, SD with diabetes induced with streptozotocin, SD sympathectomized with 6-hydroxydopamine, spontaneously hypertensive rats (SHR), SHR treated with capsaicin to prevent hypertension development, Wistar Kyoto rats (WKY), and WKY treated with capsaicin. Examination of the jejunal arteries from these rats at 12 weeks of age following normal development, or 8 weeks of hypertension development, or 8 and 12 weeks of diabetes, showed that increased innervation occurred in the SHR under all conditions, and in the diabetic rats after 8 weeks of diabetes. Medial hypertrophy occurred in the SHR and in the SD hypertensive only. It is concluded that the special relationship which exists between the sympathetic innervation and arterial media in the SHR does not occur during hypertension development in the SD rat, nor is it necessary for normal medial development in the SD rat. The sympathetic innervation does appear to have a trophic influence on vascular smooth muscle of diabetic rats, at least in the early stages of the disease.

Multiple-locus heterozygosity and the physiological energetics of growth in the coot clam, Mulinia lateralis, from a natural population

The relationship between individual energy budgets and multiple-locus heterozygosity at six polymorphic enzyme loci was examined in Mulinia lateralis. Energy budgets were determined by measuring growth rates, rates of oxygen consumption, ammonia excretion and clearance rates. Enzyme genotypes were determined using starch gel electrophoresis. Growth rate and net growth efficiency (the ratio of energy available for growth to total energy absorbed) increased with individual heterozygosity. The positive relationship between observed growth and multiple-locus heterozygosity was associated with a negative relationship between routine metabolic costs and increasing heterozygosity. Reduction in routine metabolic costs explained 60% of the observed increased growth of more heterozygous individuals. When routine metabolic costs were standardized for differences in feeding rates, these standard metabolic costs explained 97% of the differences in growth rate. Lower standard metabolic costs, associated with increasing heterozygosity, have been proposed as a physiological mechanism for the relationship between multiple-locus heterozygosity and growth rate that has been reported for a variety of organisms, ranging in diversity from aspens to humans. This study demonstrates that reduction of standard metabolic costs, at least in clams, accounts for virtually all of the differences in growth rate among individuals of differing heterozygosity.

The postnatal development of blood vessels in the optic nerve of normotensive and hypertensive rats

The blood vessels in the optic nerve of normotensive and hypertensive rats have been examined at 2, 4, 8 and 12 weeks of age. The pattern of development was found to be different in the two strains, with the number of blood vessels in the hypertensive rat optic nerve being lower at 2 weeks, but greater at 12 weeks than the normotensive rat. There appeared to be no correlation between vascularity and either myelination or changes in the fibre diameter spectrum at the ages studied. It is concluded that while the cause of the increased vascularity of the optic nerve in hypertensive rats is not known, it appears to be without effect in the structural development of the optic nerve.

The development of two subnuclei of the nucleus tractus solitarius in spontaneously hypertensive rats

Changes in relative metabolic requirements and neuronal densities in the nucleus commissuralis (NC) and nucleus medialis (NM) of the nucleus tractus solitarius were studied in spontaneously hypertensive rats (SHR) during development. The changes in relative metabolic requirements in the two subnuclei of SHR between 2 and 12 weeks of age were similar to those previously reported for normotensive WKY at the same ages. However, the relative metabolic activity in the NC of 2- and 4-week SHR was significantly higher than in normotensive rats. The differences in metabolic requirements of the NC could not be explained by differences in the neuronal densities of this subnucleus in young SHR and may reflect abnormalities in developmental or functional activities in the pre-hypertensive rat. Neuronal densities in the NC of 8- and 12-week SHR and in the NM of 4-, 8- and 12-week SHR were significantly higher than in WKY controls. Differences in the neuronal densities in the NC and NM of SHR may be explained by a smaller brain size characteristic of this strain, but differences in the NC of SHR suggest that the alterations may underlie or result from the cardiovascular abnormalities associated with the spontaneous hypertension of this strain.

The postnatal metabolic development of the nucleus commissuralis and nucleus medialis of the nucleus tractus solitarius

The ontogeny of the metabolic requirements in the nucleus commissuralis (NC) and nucleus medialis (NM) of the nucleus tractus solitarius was studied in the postnatal rat using the [3H]2-deoxy-D-glucose autoradiography technique. It was found that the metabolic requirements in the NC and NM are not constant between 2 and 12 weeks of age. A high level of metabolic activity at 2 and 8 weeks is contrasted by a lower level at 4 and 12 weeks. The apparent changes in metabolic requirements are not related to the changes in blood pressure of the rats or neuronal densities of the subnuclei which occur as the rats mature, or to exchange vessel densities of the subnuclei. Thus the higher energy requirements of the NC and NM at 2 and 8 weeks of age suggest that developmental and/or functional processes are more active at these stages.

The correlation between the development of sympathetic innervation and the development of medial hypertrophy in jejunal arteries in normotensive and spontaneously hypertensive rats

The catecholaminergic innervation of jejunal arteries was examined during development in normotensive and hypertensive rats. It was determined that a hyperinnervation of jejunal vessels in the hypertensive rats is present from 2 weeks of age onwards, before significant elevation of blood pressure and medial hypertrophy of jejunal arteries occurs. It is concluded that this hyperinnervation may be causally related to the medial hypertrophy in arteries of hypertensive animals.

Stool viruses in babies in Glasgow. 4. Further hospital studies

The events occurring during the time in hospital of 24 babies were recorded in detail, particularly those related to bowel function. The babies were admitted to a general paediatric unit with various diagnoses a total of 27 times during a six month period. The purpose of the study was to fill gaps in the records of a previous study (Scott et al. 1979) and to try to relate excretion of viruses detectable by electron microscopy to disturbances of bowel function (diarrhoea and/or vomiting). The results showed that a variety of viruses were associated with gastroenteropathy, that virus excretion could occur without disease and that hospital acquisition of virus is not uncommon. Antiobiotic treatment did not appear to precipitate diarrhoea in this small number of babies.

Factors involved in the control of RNA synthesis during regeneration of the optic nerve in the frog

The incorporation of tritiated uridine into retinal ganglion cells was studied following intra- and extracranial section of the optic nerve in the frog. It was found that incorporation increased to above control levels by two days following extracranial section of the optic nerve and by two weeks following intracranial section and was maintained at an elevated level until the regenerating optic nerve reached the diencephalon, at which point the rate of incorporation fell back to control levels. It is suggested that the signal for turning off increased uridine incorporation lies in the diencephalon, and that functional reconnection is not the signal.