Criteria-Based Assessment of a Teleophthalmology Diabetic Retinopathy Evaluation Program in a Primary Care Setting

Background:Studies have shown that teleophthalmology programs using a nonmydriatic camera in primary care settings can improve rates of diabetic retinopathy (DR) screening. However, such programs are not yet widespread due to common challenges in sustainability.Purpose:To comprehensively evaluate clinical and operational measures of an urban primary care clinic's 1-year pilot teleophthalmology DR evaluation program.Materials and Methods:This retrospective analysis used five metrics to evaluate the program: clinical diabetic retinal exam (DRE) rate, visual acuity and pathology, camera utilization, billing and insurance reimbursements, and outcomes of follow-up referrals.Results:Two hundred eleven patients were screened over 14 months. The DRE rate had more than doubled (34-75%). Of the patients, 55.9% had vision better than 20/50 in each eye and 21% with at least 1 eye worse than or equal to 20/70. DR was noted in 11% of patients. The program's first few months saw greatest camera use. Government and Medicare Advantage insurers were significantly (p < 0.001) less likely to reimburse than commercial insurers. Twenty-seven percent of patients screened had documented follow-up with an eye care provider within 16 months of their screening. Patients diagnosed with DR or recommended follow-up within 1 month were significantly (p < 0.001) more likely to schedule an appointment.Discussion:Challenges to program sustainability include efficient utilization, reimbursement from governmental insurers, and adherence to follow-up recommendations.Conclusions:Assessing teleophthalmology programs with the aforementioned five metrics allows for a comprehensive evaluation of impact and sustainability. This may be utilized to standardize the implementation and evaluation of such programs across diverse settings.

The Association between Gestational Age and Risk for Long Term Ophthalmic Morbidities among Offspring Delivered in Different Preterm Subgroups

Objective: To investigate whether there is a linear association between the degree of prematurity and the risk for long-term ophthalmic morbidity among preterm infants. Study design: A population-based, retrospective cohort study, which included all singleton deliveries occurring between 1991 and 2014 at a single tertiary medical center. All infants were divided into four groups according to gestational age categories: extremely preterm births, very preterm births, moderate to late preterm births and term deliveries (reference group). Hospitalizations of offspring up to 18 years of age involving ophthalmic morbidity were evaluated. Survival curves compared cumulative hospitalizations and regression models controlled for confounding variables. Results: During the study period, 243,363 deliveries met the inclusion criteria. Ophthalmic-related hospitalization rates were lower among children born at term (0.9%) as compared with extremely preterm (3.6%), very preterm (2%), and moderate to late preterm (1.4%) born offspring (p < 0.01; using the chi-square test for trends). The survival curve demonstrated significantly different hospitalization rates between the gestational ages (p < 0.001). The regression demonstrated an independent risk for ophthalmic morbidity among extremely preterm born offspring (adjusted hazard ratio 3.8, confidence interval 1.6−9.2, p < 0.01), as well as very preterm and moderate to late preterm (adjusted hazard ratio 2.2 and 1.5, respectively) as compared with term deliveries. Conclusions: The risk for long-term ophthalmic-related hospitalization of preterm offspring gradually decreases as the gestational age increases.

The Current Online Face of U.S. Academic Ophthalmology

Purpose To evaluate the comprehensiveness and navigation ease of online content from Web sites of U.S. academic ophthalmology departments.

Design Cross-sectional analysis of 117 U.S. academic ophthalmology department Web sites from October 1 to October 31, 2017.

Methods Data were obtained on various categories, including: clinical access and subspecialty services, social media, patient support and accessibility, residency and fellowship details, and research and faculty characteristics. Percent of Web sites possessing each feature was calculated. In addition, a comparison of content completeness and navigation metrics of Web sites between the US News and World Report top 13 ranked departments and the remaining 96 that possess an ophthalmology residency was performed.

Results Greater than 80% of Web sites list a basic core of information online: address, contact information, resident and faculty characteristics, and clinical expertise. However, only 69.2% have capabilities to donate online and 59.8% supply educational material for common eye conditions. Less than half of institutions list emergency and trauma, oncology, and low-vision rehabilitation services; only 49.6% provide a social network platform. Strikingly, accessibility features are limited; scalable text, changeable color, and multilingual capabilities are available in 20.5, 4.3, and 8.5% of Web sites, respectively. In the comparison of top 13 departments with the remaining 96, the high-ranking departments possess more Web site features, but are just as efficient to navigate.

Conclusion U.S. academic ophthalmology departments in 2017 provide a basic foundation of online content, but few contain abundant features from the viewpoints of different users.

Periodontal innate immune mechanisms relevant to obesity

Obesity affects over 35% of the adult population of the USA, and obesity-related illnesses have emerged as the leading cause of preventable death worldwide, according to the World Health Organization. Obesity's secondary morbidities include increased risk of cardiovascular disease, type II diabetes, and cancer, in addition to increased occurrence and severity of infections. Sedentary lifestyle and weight gain caused by consumption of a high-fat diet contribute to the development of obesity, with individuals having a body mass index (BMI) score > 30 being considered obese. Genetic models of obesity (ob/ob mice, db/db mice, and fa/fa rats) have been insufficient to study human obesity because of the overall lack of genetic causes for obesity in human populations. To date, the diet-induced obese (DIO) mouse model best serves research studies relevant to human health. Periodontal disease presents with a wide range of clinical variability and severity. Research in the past decade has shed substantial light on both the initiating infectious agents and host immunological responses in periodontal disease. Up to 46% of the general population harbors the microorganism(s) associated with periodontal disease, although many are able to limit the progression of periodontal disease or even clear the organism(s) if infected. In the last decade, several epidemiological studies have found an association between obesity and increased incidence of periodontal disease. This review focuses on exploring the immunological consequences of obesity that exacerbate effects of infection by pathogens, with focus on infection by the periodontal bacterium Porphyromonas gingivalis as a running example.

NK-1 antagonist reduces colonic inflammation and oxidative stress in dextran sulfate-induced colitis in rats

Although substance P (SP) has been implicated as a mediator of neurogenic inflammation in the small intestine, little information is available regarding the role of SP in the pathogenesis of chronic ulcerative colitis. In this study, our aim was to investigate whether the intraperitoneal administration of a nonpeptide neurokinin-1 (NK-1) antagonist, CP-96345, which antagonizes the binding of SP to its NK-1 receptor, results in the attenuation of colonic inflammation induced in rats by 5% dextran sodium sulfate (DSS) in drinking water for 10 days compared with an inactive enantiomer, CP-96344. Disease activity was assessed daily for 10 days, after which colonic tissue damage was scored and myeloperoxidase activity and colon and urinary 8-isoprostanes were measured. Animals receiving DSS exhibited marked physical signs of colitis by day 5 compared with controls. Chronic administration of the NK-1 antagonist significantly reduced the disease activity index, mucosal myeloperoxidase activity, colonic tissue damage score, and mucosal and urinary levels of 8-isoprostanes compared with inactive enantiomer- or vehicle-injected (saline) animals receiving DSS alone. These data indicate that the administration of an NK-1 antagonist can attenuate colonic inflammation and oxidative stress and suggest a novel therapeutic approach in the treatment of chronic ulcerative colitis.

Actions of intrathecal diphtheria toxin-substance P fusion protein on models of persistent pain

Substance P (SP) plays a central role in the transduction of second messenger signals from primary afferent nociceptive terminals to second-order neurons in the spinal cord. We have tested a recombinant engineered diphtheria toxin/SP fusion protein (DAB389SP) in acute and chronic pain models in the rat. DAB389SP binds to the SP receptor (SPR) and is internalized and kills SPR-expressing cells by blocking cellular protein synthesis. DAB389SP delivery was by intrathecal infusion, of varying duration, at the lumbar level. In the chronic constriction injury model of neuropathic pain a significant reduction in mechanically induced hyperalgesia was obtained. This effect was less marked in an acute carageenan inflammation model. Although other pain characteristics (mechano-allodynia, cold-allodynia, and heat-hyperalgesia) showed some improvement, these were less pronounced. Immunocytochemistry revealed a toxin-induced reduction in lamina I, of SPR and of NMDA NR1 subunit receptor expressing neurons, and of c-Fos, an inducible molecular marker of persistent nociceptive activity. The use of cytotoxic fusion proteins to target specific cell types may be of considerable benefit in the study of nociception and the treatment of chronic pain.

Periodontal disease activity: a development strategy for its investigation by means of accurate 3-dimensional clinical measurement

The central problem in all previous approaches to clinical assessment of periodontal disease activity is the use of unidimensional measurement, which implies a number of unjustifiable assumptions. In addition, the use of unidimensional probing measurement has established that there are several distinct problems of validity and reliability in currently available techniques. The present paper begins with an analysis of these matters, leading to an approach to accurate clinical measurement of periodontitis in 3 dimensions, with the possibility of future development of a valid system for assessing the nature of disease activity.

Nonparametric estimation of ultrasound pulses

An algorithm for nonparametric estimation of 1-D ultrasound pulses in echo sequences from human tissues is derived. The technique is a variation of the homomorphic filtering technique using the real cepstrum, and the underlying basis of the method is explained. The algorithm exploits a priori knowledge about the structure of rf line echo data and can employ a number of adjacent rf lines from an image. The prime application of the algorithm is to yield a pulse suitable for deconvolution algorithms. This will enable these algorithms to properly take into account the frequency dependence of the attenuation and its variation within a patient and among patients. It is also possible to use the estimated pulse for attenuation estimation, and the consistency of the assumptions underlying the proposed technique is demonstrated by its ability to recover low variance attenuation estimates in the normal liver from in vivo pulse-echo data. Estimates are given for eight different patients.

Assessment of hybrid speckle reduction algorithms

A consequence of employing coherent detection methods in medical ultrasound imaging systems is the occurrence of interference effects in the received echo field, which produce the speckle artefact. Speckle can severely degrade the information content of the image, and its efficient removal from ultrasound pulse-echo images is the focus of a number of research projects. Traditionally, the approach towards speckle reduction in pulse-echo images has been based on two classes of technique, either employing some form of spatial/frequency compounding or a data (image) filter. Both approaches have inherent shortcomings, and two alternative techniques are suggested here: 'local frequency diversity' and 'frequency differencing'. These algorithms deterministically identify where speckle occurs, and correct for speckle only within short, localized, corrupted segments of the A-line. This provides the potential for real-time implementation. Simulated and clinical in vivo images have been obtained, and the capabilities of the alternative speckle reduction algorithms are assessed against the more conventional approaches.

[Lipedema]

An overall view of the clinical findings in lipedema is given and of its treatment. Lipedema is shown to be a distinct illness, and not just a disturbance of the distribution pattern of subcutaneous fatty tissue. The diagnosis is based on an accurate history and specific criteria on clinical examination and palpation.

Reflections on tissue characterisation

Theoretical predictions that absorption and velocity dispersion, in addition to characteristic acoustic impedance mismatch, mediate the reflectivity of a planar interface are explored. A technique to measure the frequency dependence of the reflectivity is described: a special hydrophone, purpose-built to this end, is utilised in order to show that perspex/water and neoprene/water reflectivities are not inconsistent with the general predictions of the theory. An approach towards displaying, simultaneously, both the temporal and spectral properties of ultrasound pulses is described, and its potential utility in both reflectivity measurement and investigation of non-linear propagation is proposed.

Phasing out speckle

It is demonstrated that the instantaneous frequency of a backscattered echo sequence can be used to pinpoint the location of destructive interference effects. These interference artefacts, which are generally interpreted as speckle in the image, are generally removed by stochastic averaging or filtering methods applied to the acquired image. The method proposed here can detect such artefacts within individual A-lines, and thus differs from conventional techniques. Where speckle is recognised within each A-line, the artefact can be corrected on a local basis by the application of the frequency diversity technique. Because it relies only on A-line processing, the approach points the way towards a speckle reduction technique which can realistically be implemented on a real-time basis. In this paper, the principles of the technique are illustrated using a simple two-reflector model.

Substance P and neurokinin A in the cat carotid body: localization, exogenous effects and changes in content in response to arterial pO2

In the present work we studied the occurrence of substance P (SP) and neurokinin A (NKA) in the carotid bodies of cats by means of immunocytochemistry and radioimmunoassay (RIA). We also compared the exogenous effects of SP and NKA on carotid body sensory discharge. SP- and NKA-like immunoreactivities (SP-LI; NKA-LI) were seen in many glomus cells and in a sparse plexus of fine fibers. The SP-LI containing glomus cells and fibers also exhibited NKA-LI, suggesting that both these tachykinins coexist in the carotid body. Chemoreceptor discharge increased both by SP and NKA in a dose-dependent manner. The peak excitation produced by SP and NKA was the same when the effects were compared on an equimolar basis. The tachykinin content of the carotid bodies varied with changes in arterial pO2. During normoxia, SP and NKA levels were 57 +/- 8 and 85 +/- 14 fmol/mg, respectively. When the animals were exposed for 1 h to 100% O2, SP content was unchanged (51 +/- 4 fmol/mg), whereas NKA levels were significantly lower than during normoxia (29 +/- 3 fmol/mg, P less than 0.01). Following 1 h of hypoxia, SP content of the carotid body was 146 +/- 20 fmol/mg, a value higher than that obtained during normoxia and hyperoxia. NKA levels, on the other hand, were not significantly different from normoxic values. These results indicate that the cat carotid body (1) contains both SP and NKA, (2) both peptides augment neural discharge of the carotid body and (3) their levels in the carotid body are substantially altered by arterial oxygen, the natural stimulus to the chemoreceptors.

Quantitative sonography of muscle

Ultrasound imaging allows detection of pathologic change in muscle on the basis of increased strength of echoes. With current commercial equipment, however, there is no method of quantitation of the echoes representing muscle, and there is lack of uniformity in scanning methodology. We describe a specially constructed scanning system, designed to access the raw echo data directly from the ultrasound transducer, and allow display and measurement of the echo signals on a computer. In a study of 38 boys with Duchenne muscular dystrophy, aged 1 to 11 years, who had an ultrasound scan of the thigh muscle, 32 (84%) had abnormality on quantitation of the ultrasound echoes. The quantitative techniques we describe could easily be incorporated into the design of ultrasound scanners.

Acute reduction of brain substance P induced by nicotine

Ten minutes after a single injection of 0.8 mg/kg nicotine SC (free base) the level of substance P-like immunoreactivity (SPLI) was reduced by 61-73% in rat caudate-putamen, nucleus accumbens, and olfactory tubercle, with smaller and not significant reductions in the frontal cortex, substantia nigra, and ventral tegmental area. The nicotinic receptor antagonist mecamylamine (1.0 mg/kg IP) prevented the reductions in SPLI. The rapidity and the degree of the changes in SPLI after nicotine exceed those previously reported for other agents and implicate substance P neurotransmission as a major component of nicotinic action.

Noninvasive evaluation of hepatic fibrosis using frequency demodulation of ultrasound signals

A new ultrasound image can be produced by frequency demodulation (FM) of the conventional ultrasound signal. This new FM image appeared to produce a more accurate representation of the fine structure of the liver. The individual features of the FM image were correlated with hepatic portal fibrosis and cirrhosis on liver biopsy in 34 patients with minimal hepatic fat and sinusoidal collagen. An overall ultrasound score correlated with portal fibrosis (r = 0.788; P less than 0.001). We conclude that the FM image may be helpful in measuring and following the progression of hepatic fibrosis in patients with chronic liver disease.

Frequency-demodulated US: evaluation in the liver. Work in progress

Frequency modulated (FM) imaging is a new ultrasound (US) modality that uses pulse-echo signal instantaneous frequency in addition to the conventional envelope information. Eight features of the FM image in nondiseased livers are described. The technique is evaluated in a study of 34 patients with biopsy-proved diffuse liver disease. Visual grading of FM US image features shows good correlation with levels of biopsy-graded hepatic fibrosis. Patients with diffuse parenchymal liver disease often exhibit evidence of the abnormality when FM liver imaging is used, while such evidence is not as well demonstrated with conventional envelope (AM) imaging.

Attachment of fibroblasts following hyperthermia and ultrasound

The rate of cell attachment to the culture substratum is reduced in mouse L cells by hyperthermia at 44 degrees C. The time for 50 per cent attachment of the cells increases rapidly with increasing time of heating immediately before assay. The rate of attachment after 44 degrees C does not show a linear correlation with clonogenic survival, ruling out the use of attachment as a rapid assay of clonogenic survival. The attachment process is less sensitive to heat in cells made thermally tolerant by a prior heat treatment. In contrast, ultrasound irradiation at 37 degrees C and below the cavitational threshold (1.5 MHz, 2.2 W/cm2, 15 min) did not alter the rate of attachment, but at 44 degrees C, ultrasound decreased both clonogenic survival and the rate of attachment to a much greater extent than 44 degrees C alone. As the temperature increase caused by the ultrasound was less than 0.5 degrees C, the data provide evidence of a non-thermal component of ultrasound damage.

Ultrasound imaging in the diagnosis of muscle disease

A comparative study has been done of the static B-scan ultrasound appearance of the quadriceps muscle of the thigh in 60 new patients attending our muscle clinic and in 60 control children. In the control subjects there was good visualization of bone and fascia, which stood out clearly against the background of echo-free muscle tissue. Striking change was found in children with neuromuscular disease. Muscular dystrophies were associated with an increase in the intensity of echo reflected from the muscle substance, with corresponding loss of bone echo. Spinal muscular atrophies and neuropathies also showed an increase in muscle echo along with atrophy of the muscle and increase in depth of subcutaneous tissue. Various congenital myopathies also showed changes. Infants with hypotonia from nonneuromuscular causes had normal scans. Severity of change on the scan did not relate to functional disability, and some children had good function yet strikingly abnormal scans. Three degree of change on the scan correlated with the degree of disruption of muscle architecture on biopsy. Ultrasound imaging has proved to be a useful, noninvasive screening tool in the investigation of children with neuromuscular disease.

Cavitational bio-effects of 1.5 MHz

The effects of continuous wave ultrasound on three different classes of biosystems have been investigated at a frequency of 1.5 MHz. The criteria for cavitation are given, and these are applied to experimentally observed growth retardation of plant roots, cell death and DNA degradation in bacteria and pyknosis of human lymphocytes. An attempt is being made to find common physical mechanisms for all these biological responses, and cavitation processes in particular are examined here. A description is given of the techniques used to monitor the presence of cavitation, and indirect evidence, drawn from pulsed field and elevated pressure experiments, is presented to show that other-non-linear processes are also operative.

Detection of pathological change in dystrophic muscle with B-scan ultrasound imaging

A comparative study of the ultrasound appearances of the thigh with the static B scan showed consistent differences in 10 children with muscular dystrophy compared with 40 healthy controls. This non-invasive technique could be useful in assessing the extent of pathological change in dystrophic patients and could prove a valuable diagnostic aid.

Ultrasound pulse propagation in dispersive media

Human tissues show dispersive ultrasound absorption, and it is important to understand how ultrasound pulses in the diagnostic frequency range, 1-10 MHz, propagate in such media. An uncomplicated wave-equation model for human soft tissues is postulated, and its dispersion law for absorption is demonstrated to be compatible with existing experimental findings. Propagative solutions for the simple one-dimensional, homogeneous case (no scattering) are derived. It is shown that the transmitted pulse consists of an undistorted, damped replica of the incident pulse, plus a depth-dependent, time-extended 'rumble', both of which travel at a fixed, finite velocity through the medium. The constancy of this (signal) velocity reconciles the predicted velocity dispersion with the observed weakness of such an effect in many tissues, and some consequences for the measurement of both velocity and absorption are indicated.

The reconstruction of objects from incomplete projections

The effect of an imcomplete field of view on the reconstruction of objects from their projections is considered. An exact analytical method is used to calculate the reconstruction of an impulse and an annulus which lie out the field of view of an imaging device. A general impression of the effects of truncating the projections of any object may be obtained from these calculations of elemental objects.

1.5 MHz ultrasound irradiation of human lymphocytes

Human lymphocyte cultures are exposed to 1.5 MHz continuous wave ultrasound, and it is demonstrated that cell death, as monitored by pyknosis, follows immediately on sonication at intensities within the usual therapeutic range (less than 1.7 W/cm2,spatial average). The number of cells affected is determined by the ultrasound intensity only, but the rate at which they proceed through their pyknosis cycle is modified by both the intensity and the duration of exposure. There is a clear indication of an intensity threshold for the effect approximately 1.1 W/cm2. Pulsed 1.5 MHz ultrasound (70 mus, 1 :1 pulses, 1.7 W/cm2 space-time average) results in a 15-20 hour delay in the measurable response to sonication. It is shown that the intracellular presence of a lysosomal-enzyme inhibitor strongly modifies the course of the ultrasound action. Evidence is presented to suggest that the basic interaction mechanism is via a cavitation process, but there are some difficulties with this interpretation, which are also discussed.

Transfer functions for describing ultrasound system performance

A practical method of assessing ultrasonic A-scan pulse-echo scanner performance is described, which relies upon the identification and quantitation of an overall system transfer function. The mapping of reflecting elements into an image is then described by this transfer function, and indices of system performance, and particularly resolution and range accuracy, are developed in terms of the shape of the transfer function. Some advantages of this method compared to more conventional methods of assessing scanner performance are discussed.

The intestine as source of immunoreactive substance P in plasma of the cat

1. Substance P (SP) was measured in acid acetone extracted plasma of cats using a sensitive radioimmunoassay. The immunoreactive material was submitted to ion exchange chromatography and at least 90% of immunoreactivity co-chromatographed with synthetic SP. 2. The level of immunoreactive SP (I-SP) in extracted plasma of the cat was 69.3 +/- 9.8 fmol/ml with values ranging from 2.5 to 165 fmol/ml. Evisceration of the cats caused a decrease of I-SP levels from 70.8 +/- 30.8 fmol/ml to 20.8 +/- 9.9 15 min and to 26.8 +/- 19.7 fmol/ml 60 min after the operation. 3. Ligation of intestinal blood vessels led to a fall in I-SP levels from 58.7 +/- 11.5 to 25.9 +/- 4.1 fmol/ml within 15 min. 4. No difference between I-SP values in portal (71.8 +/- 11.2 fmol/ml) and peripheral plasma (68.3 +/- 12.1 fmol/ml) was found under the conditions in which these experiments were performed. 5. It is concluded that a major part of circulating immunoreactive SP originates from the intestine.

Echo structure in medical ultrasonic pulse-echo scanning

The factors contributing to the structure (i.e. amplitude and shape) of echoes from major reflecting boundaries in tissues are reviewed. It is shown that the pulsed nature of a scanner's emitted sound field introduces complex variations in echo shape which are not usually taken into account. Moreover, echo structure is strongly modified by the geometry of the interface and not only by the physical composition of the adjacent materials. These effects are shown to be characteristic of the basic reflection process with pulsed fields. The influence of some receiver transfer properties on the displayed echo is also indicated. It is suggested that the analysis of sound fields scattered from small-scale internal structures (echo ensemble analysis) is a preferred method of tissue characterization.

Neurotensin: specific binding to synaptic membranes from rat brain

The binding of neurotensin to synaptic membranes from rat brain was studied at 24 degrees with the use of [3H]neurotensin. The binding was found to be highly specific, saturable, and reversible. Values for KD of 2 nM and 0.9 nM were derived from equilibrium and kinetic experiments, respectively. Virtually no degradation of neurotensin was observed in the incubation medium after exposure to synaptic membranes under the conditions of the binding studies. Competitive inhibition of [3H]neurotensin binding by partial sequences of neurotensin revealed that the addition of the residue arginine-8 to the neurotensin-(9-13)-pentapeptide increases about 500-fold the relative binding potency, whereas the remaining portion of the NH2-terminal region is mainly responsible for full pharmacological potency; the COOH-terminal leucyl residue is essential for binding.

Ultrasonic backscattering from human tissue: a realistic model

The propagation of ultrasound pulses in inhomogeneous media is described, and it is shown that they are scattered by fluctuations in density and compressibility. It is proposed that some of the echoes recorded by diagnostic pulse echo equipment are produced in this way. The precise form of the acoustic field backscattered from tissues is calculated using realistic approximations about the nature of tissue inhomogeneitics and the form of the pulses used. It is shown that only limited information about tissue structure is contained in these signals, and the restrictions imposed by the use of typical pulses are indicated. The implications of this analysis for methods of tissue characterization and clinical imaging are discussed.

Non-invasive left ventricular volume determination by two-dimensional echocardiography

Twenty patients undergoing routine left ventricular single-plane angiography have been investigated by an ultrasonic triggered B-scan technique to provide a two-dimensional cross-sectional image of the left ventricle in end-systole end-diastole. An area-length method has been used to establish the correlation between the angiographic and the echocardiographic assessments of left ventricular chamber volume (r equals 0.88) and ejection fraction (r equals 0.81). Differences between the two techniques are discussed, and it is concluded that in approximately 80 per cent of patients triggered B-scanning may provide a safe, non-invasive, and convenient technique for the determination of volumes and certain functional parameters, especially in patients with dilated hearts and irregular left ventricular shape, where M-scanning is known to be less reliable.

Homologous radioimmunoassay of thyrotrophin in rat plasma

An homologous radioimmunoassay (RIA) using the highly purified rat thyrotrophin (TSH) and anti-rat TSH recently made available by NIAMDD is described in detail.

Evidence that the assay measures TSH and only TSH includes the following:

Findings for T4-treated rats and saline-treated controls show that the homologous RIA is more sensitive than previous, heterologous assays: In previous studies, plasma TSH levels of most or all of rats treated with T4 were not clearly greater than zero. By contrast, in the homologous RIA reported here, values for such rats did not overlap the range of the zero point on the one hand, nor the range for saline-treated controls on the other. Thus, distinct ranges were defined for both normal and low TSH levels. In view of the 1:20 final dilution of plasma during assay, it does not seem likely that non-specific effects of plasma were primarily responsible for the low TSH values of T4-treated rats.

Additionally, the useful range of the homologous assay (about 200-fold) is greater than that of earlier assays (about 70-fold, or less). Finally, the use of highly purified rat TSH for standards has avoided inconsistencies previously encountered with bovine TSH standards.