Lack of biological activity of preproendothelin [110-130] in several endothelin assays

A 21 amino acid peptide containing the prepropendothelin sequence from amino acids 110 to 130 and two intrachain disulfide bonds was synthesized and tested for biological activity in the following endothelin assays: 1.) a competition binding assay using [125I]ET-1 and dog heart membranes, 2.) three RIA's using 125I-ET-1, -2 and -3 and the respective anti-ET rabbit antisera; and 3.) a contractile activity bioassay using hamster aortic rings. The synthetic peptide which has been referred to as the "endothelin-like" peptide occurs 36 amino acids C-terminal to endothelin in the prepro-protein sequence. It contains only 40% sequence homology to the three endothelin isoforms, but has the same sequence and cyclization pattern of cysteines at positions 1, 3, 11 and 15. Despite the overall similarity in secondary structure to the three isoforms of endothelin and sarafotoxin S6b, preproendothelin [110-130] had no activity in any of the assays when tested at concentrations of 10(-10)M to 10(-5)M.

Total body irradiation for bone marrow transplantation: the Memorial Sloan-Kettering Cancer Center experience

In May 1979, Memorial Sloan-Kettering embarked on a programme of hyperfractionated TBI (HFTBI), 1320 cGy in 11 fractions over 4 days with partial lung shielding (1 HVL), followed by cyclophosphamide (60 mg/kg/d x 2d) for cytoreduction prior to allogeneic bone marrow transplantation (BMT). Anterior and posterior chest wall electron "boosts" were given to the areas blocked (600 cGy in 2 fractions) on the last two days of treatment. Since then, we have treated over 600 patients with HFTBI, the majority for allogeneic BMT. Several modifications have occurred over the years. We have added a "boost" electron dose of 400 cGy to the testes in all male leukemic patients; this reduced testicular relapses from a rate of 14% (4/28) to 0%. In an attempt to increase engraftment of T-depleted BMTs, we added one additional fraction; since our present dose/fraction was also increased to 125 cGy, we now deliver a total dose of 1500 cGy in 12 fractions over 4 days for allogeneic transplants. Tolerance to HFTBI has been excellent relative to the single dose (SD) regimen utilised prior to May, 1979. The incidence of fatal interstitial pneumonitis (IP) decreased from 50% in the SD regimen to 18% after the introduction of HFTBI. In children, the incidence of IP was only 4% with HFTBI. With the introduction of T-depleted marrows, fatal IP in adults has decreased also, e.g. to less than 10% in CML patients. With conventional BMT after HFTBI, relapse at 5 years has been exceedingly low (e.g. in children, 13% for ALL, 2nd remission and 0% for AML, 1st remission) and engraftment has been 100%. With matched T-depleted BMT, rejections have occurred in 15% overall; the incidence of graft failure has not been reduced by the higher dose of HFTBI. Relapses in this setting are equivalent to relapses with conventional BMT for AML, but appear to be increased for ALL. Radiobiological findings related to HFTBI will also be discussed.

Myocardial protection by simple systemic hypothermia without aortic occlusion

Systemic hypothermia at 25 degrees-28 degrees C without chemical cardioplegia was used in 908 patients undergoing coronary artery bypass grafting. Local coronary artery flow was interrupted only during grafting of a distal anastomosis. Systemic perfusion pressure was maintained at 80-100 mmHg, hematocrit at 20%-25%, and pCO2 and pH were monitored during hypothermia according to the alpha-stat principle, while the left ventricle was vented routinely. Proximal anastomoses were performed just before extracorporeal circulation was started by only partially occluding the ascending aorta. Preoperatively 61.9% of the patients had had a myocardial infarction, and 44% had unstable angina. In 14% a severe lesion of the main stem of the left coronary artery was present. Left ventricular function was moderately depressed in 25% and severely depressed in 8% of the patients. Forty-eight patients (5.3%) were aged 70 years or older. The mean number of grafts placed per patient was 3.3. Perioperative myocardial infarction occurred in 3%. Death due to left ventricular failure occurred in 0.4%. No left ventricular assist devices were needed; an intra-aortic balloon pump was used in 1%; positive inotropic support was required in 3.8% of the patients. These results indicate that systemic hypothermia alone provides safe myocardial protection and in certain cases may be the method of choice, particularly if aortic cross clamping or administration of cardioplegic solution is contraindicated. In addition, this method provides rapid revascularization of a severely ischemic zone, as present after unsuccessful PTCA procedures.

Dose computations for three-dimensional radiation treatment planning

The knowledge of radiation dose at all points of interest within a patient's body is essential for the evaluation of treatment plans and for the judicious selection of the best one from among a set of competing plans. This paper discusses the physical and geometric aspects of radiation dose distribution calculations necessary for three-dimensional treatment planning. A practical method of obtaining dose distributions for a given arrangement of beams and beam modifiers is with the aid of computer calculations based on mathematical formalisms derived from the principles of physics. The most accurate method of computing dose is by Monte Carlo stimulation of radiation transport. However, this method is extremely CPU time intensive and too complicated to implement for routine radiation treatment planning. Approximate semi-empirical methods have to be employed to compute dose distributions within reasonably short times. Conventional approximate methods do not yield results of adequate accuracy. Newer methods that are better able to take into account the three-dimensional nature of radiation transport have been introduced but require considerably greater computing capacity. Furthermore, computing power needs for dose calculations for three-dimensional treatment planning are one to two orders of magnitude greater than the corresponding needs of two-dimensional treatment planning. However, the concern for greater computing power requirements is being lessened somewhat with the advent of high speed computers and specialized hardware, and with the development of clever algorithms for speeding up dose calculations. For three-dimensional treatment planning some geometric issues, such as the calculation of dose at points in three-dimensional space, the incorporation of three-dimensional patient and beam geometry into a system for dose calculations, the choice of optimum grid spacing, radiological pathlength calculations, and algorithms for speeding up dose calculation, take on added importance compared to the corresponding issues for conventional two-dimensional planning. These issues are also discussed here briefly.

Autonomic function tests in cases of chronic severe anaemia

Autonomic functions were studied in 30 adult cases of chronic severe anaemia (CSA) and equal number of age and sex matched healthy controls. Blood pressure and heart rate responses to standing, to respiration (expiratory-inspiratory ratio), to Valsalva manoeuvre (Valsalva ratio) and to hand immersion in ice cold water and given 1.8 mg of atropine intravenously were studied. Patients with CSA had significantly high basal pulse rate and low blood pressure as compared to control subjects (p less than 0.001). The expiratory inspiratory ratio was abnormal in 30% of the cases of CSA (p greater than 0.10) valsalva ratio was abnormal in 50% of cases (p less than 0.01) and postural tachycardia was observed in 60% of cases (p less than 0.001). Normal response to hand immersion in ice cold water was observed in 56.6% of cases (p less than 0.001). Atropine resulted in tachycardia in 73.4% of cases of CSA as compared to 86.7% of controls (p less than 0.10). All the cases of CSA showed one or more abnormal response and in 16.6% of cases all responses were abnormal.

Comparative efficacy of atenolol and labetalol in essential hypertension--a double blind cross over trial

In a double blind cross-over drug trial, antihypertensive effects (resting and after dynamic exercise) of atenolol and of labetalol were studied in 20 patients of mild to moderate essential hypertension. Both drugs exhibited almost equal antihypertensive response, and were well tolerated. Haemodynamic variables (HR, SBP, DBP and RPP), both at rest and after maximal tread mill exercise, were significantly altered (P less than 0.001) by both drugs. Exercise capacity was observed to be marginally improved by atenolol. Although the antihypertensive effect, when compared between the two drugs, was not statistically significant, individual suitability or comparison revealed a preference for atenolol in 17 patients and for labetalol in 3 patients.

Three-dimensional radiation treatment planning

A major aim of radiation therapy is to deliver sufficient dose to the tumour volume to kill the cancer cells while sparing the nearby healthy organs to prevent complications. With the introduction of devices such as CT and MR scanners, radiation therapy treatment planners have access to full three-dimensional anatomical information to define, simulate, and evaluate treatments. There are a limited number of prototype software systems that allow 3D treatment planning currently in use. In addition, there are more advanced tools under development or still in the planning stages. They require sophisticated graphics and computation equipment, complex physical and mathematical algorithms, and new radiation treatment machines that deliver dose very precisely under computer control. Components of these systems include programs for the identification and delineation of the anatomy and tumour, the definition of radiation beams, the calculation of dose distribution patterns, the display of dose on 2D images and as three dimensional surfaces, and the generation of computer images to verify proper patient positioning in treatment. Some of these functions can be performed more quickly and accurately if artificial intelligence or expert systems techniques are employed.

Retinopathy in insulin dependent diabetes mellitus (IDDM) in south India

The prevalence of diabetic retinopathy was assessed by direct and indirect ophthalmoscopy in a group of patients with insulin dependent diabetes mellitus (IDDM). Fourteen percent of patients had retinopathy. Proliferative retinopathy and severe background retinopathy including maculopathy were both seen in four percent of patients. It is possible that the lower prevalence rates for these complications is due to the shorter duration of diabetes in our patients.

Molecular basis of the early events in plant–fungus interaction

Fungal spores that land on aerial surfaces of plants first come into contact with plant cuticle. The cuticle is composed of an insoluble polyester called cutin, which is composed of hydroxy and hydroxyepoxy fatty acids and associated soluble waxes. The wax components can trigger differentiation of germinating fungal spores into infection structures. The penetration of the fungus into the plant requires enzymatic degradation of the polyester and the underlying carbohydrate barriers. The polyesterase, called cutinase, is induced by the contact with the plant surface. The small amount of cutinase carried by the spore generates a small amount of cutin monomers upon contact with the host, and the unique monomers trigger expression of the cutinase gene. This transcriptional level control can be demonstrated with isolated nuclei. Upon incubation of nuclei with cutin monomer and a soluble protein factor from the fungus, cutinase transcription is selectively activated. Structure activity relationships showed that the cutinase transcription activation required all of the structural elements of the cutin monomer. The cutinase transcript generated by the isolated nuclei was identical in size to the cutinase mRNA induced in the fungal cultures, which indicated usual initiation and termination. Fungal infection triggers defense reaction in plants. Plant peroxidases were implicated in the defense response of plants to fungal attack and stress. A highly anionic peroxidase involved in suberization of cell walls in tomato plants in response to fungal attack was cloned and sequenced. It was observed that in resistant lines of tomato the expression of this anionic peroxidase was induced 1 day earlier than in susceptible lines.Key words: cutinase, cutin monomers, pectate lyase, Fusarium solani pisi, anionic peroxidase.

Steroid induced glaucoma and cataract

Long term use of topical & systemic steroids produce secondary open angle glaucoma similar to chronic simple glaucoma. The increased IOP caused by prolonged steroid therapy is reversible but the damage produced by it is irreversible. In this study, we analysed 25 patients (44 eyes) with steroid induced glaucoma, who reported to us with dimness of vision, haloes and elevated I.O.P. and were using steroids for long duration due to various causes. The behaviour of the I.O.P. due to different steroid preparations, the type of lenticular change, and the management of those cases are discussed in this paper. From our study we conclude that dexamethasone and betamethasone both topical as well as systemic are more potent in producing glaucoma and cataract than medrysone and prednisolone. The condition is reversible without permanent damage when the duration of steroid therapy is short and vice versa.

Evaluation of a non-mydriatic camera in Indian and European diabetic patients

The value of the Canon CR3-45NM non-mydriatic fundus camera in screening for diabetic retinopathy has been assessed in two ethnic groups, namely, 45 Indian and 40 European diabetic patients. There was 72% agreement between ophthalmoscopy by an ophthalmologist and the photographic assessment, and 100% agreement on clinically important lesions requiring treatment. However, peripheral retinal lesions, seen on ophthalmoscopy but lying outside the photographic field, occurred in 4% of eyes. 6% of photographs were totally unassessable and an additional 12% were only partially assessable. The prevalence and severity of retinopathy was similar in Indian and European patients. The advantages and disadvantages of the non-mydriatic camera in screening for diabetic retinopathy are discussed.

A comprehensive three-dimensional radiation treatment planning system

A comprehensive software system has been developed to allow 3-dimensional planning of radiation therapy treatments using the extensive anatomical information made available by imaging modalities such as CT and MR. Biological structures of interest and tumor volumes are defined by outlines drawn on a sequence of CT slices. Beam set-ups may then be determined in three dimensions by displaying the structure contours in a beam's eye view, or in two dimensions using a single CT cut. Each beam defined may be shaped by the specification of block aperture contours, and its intensity may be modified with the use of planar compensators. 3D dose calculation algorithms are discussed. To evaluate the calculation results, dose volume histograms are provided, as well as various types of displays in two and three dimensions, including dose on arbitrarily oriented planes, dose on the surface of anatomical objects, and isodose surfaces. Computer generated beam films are also available as an aid in patient set-up verification. These tools, and others, provide the basis for a comprehensive 3D system that can be used throughout the treatment planning process.

Pancreatic B-cell function in relation to diabetic retinopathy in Asian Indian NIDDM patients

Pancreatic B-cell function in relation to diabetic retinopathy was studied in 195 NIDDM patients with long-standing diabetes. Background diabetic retinopathy (BDR) was present in 95 (48.7%) and proliferative retinopathy (PDR) in 17 (8.7%) of the subjects. There was no significant difference between the BDR, PDR, and non-retinopathy groups with respect to age, age at diagnosis of diabetes and HbA1 values. Mean duration of diabetes was higher in the PDR group (p less than 0.05). Serum C-peptide values showed no correlation with the presence of retinopathy or with the duration of diabetes. The C-peptide values were widely scattered in patients with BDR and PDR showing no association between pancreatic B-cell reserve and occurrence or severity of retinopathy in NIDDM patients. Thus, decreased pancreatic B-cell reserve does not appear to be a risk factor for diabetic retinopathy in NIDDM patients.

Extraction of pencil beam kernels by the deconvolution method

A method has been developed to extract pencil beam kernels from measured broad beam profiles. In theory, the convolution of a symmetric kernel with a step function will yield a function that is symmetric about the inflection point. Conversely, by deconvolution, the kernel may be extracted from a measured distribution. In practice, however, due to the uncertainties and errors associated with the measurements and due to the singularities produced in the fast Fourier transforms employed in the deconvolution process, the kernels thus obtained and the dose distributions calculated therefrom, often exhibit erratic fluctuations. We propose a method that transforms measured profiles to new, modified distributions so that they satisfy the theoretical symmetry condition. The resultant kernel from the deconvolution is then free of fluctuations. We applied this method to compute photon and electron dose distributions at various depths in water and electron fluence distributions in air. The agreement between measured and computed profiles is within 1% in dose or 1 mm in distance in high dose gradient regions.

The effect of angular spread on the intensity distribution of arbitrarily shaped electron beams

Knowledge of the relative intensity distribution at the patient's surface is essential for pencil beam calculations of three-dimensional dose distributions for arbitrarily shaped electron beams. To calculate the relative intensity distribution, the spatial spread resulting from angular spread is convolved with a two-dimensional step function whose shape corresponds to the applicator aperture. Two different approaches to obtain angular spread or the equivalent spatial spread are investigated. In the first method, the pencil beam angular spread is assumed to be Gaussian in shape. The angular spread constants (sigma theta) are then obtained from the slopes of measured intensity profiles. In the second method, the angular spread, in the form of an array of numerical values, is obtained by the deconvolution of measured intensity profiles. After obtaining the angular spread, the calculation for convolution is done in a number of parallel planes normal to the central axis at various distances from the electron collimator. Intensity at any arbitrary point in space is computed by interpolating between intensity distributions in adjacent planes on either side of the point. The effects of variations in angular spread as a function of field size for two treatment machines, one with a scanned electron beam and the other with a scattering foil, have been studied. The consequences of assuming angular spread to be of Gaussian shape are also examined. The electron intensity calculation techniques described in this paper apply primarily to methods of dose calculations that employ pencil beams generated using Monte Carlo simulations.

Clinical features of diabetes in the young as seen at a diabetes centre in south India

This study reports on the clinical pattern of 545 consecutive young diabetic patients with age at onset below 30 years attending a diabetes centre in Southern India. Three hundred and fourteen patients (57.7%) were classified as having non-insulin-dependent diabetes of the young (NIDDY), 119 (22%) as insulin-dependent diabetes (IDDM) and 28 (5%) as malnutrition-related diabetes (MRDM); 4% fibrocalculous pancreatic diabetes and 1% protein-deficient pancreatic diabetes. The remaining 84 patients could not be classified into any of the above categories. A positive family history of diabetes was more common in NIDDY compared to the other groups (P less than 0.001). While 40.3% of patients with IDDM had age at onset below 15 years, the other types of diabetes were rarely seen in patients younger than this. Body mass index (BMI) did not reliably indicate the MRDM forms of diabetes as 70% of patients with IDDM also had a BMI of less than 18, one of the criteria recommended for the diagnosis of MRDM. C-peptide levels in MRDM were intermediate between the IDDM and NIDDY groups. Microvascular complications were present in all the groups of young diabetics. The frequency was higher in NIDDY patients who also had a longer duration of diabetes. There was an increasing prevalence of complications with increasing duration of diabetes.

Dose computations for asymmetric fields defined by independent jaws

Asymmetric fields defined by independent jaws can be used to split a beam or to match adjacent fields. We have extended a method originally developed for symmetric fields to calculate the dose for asymmetric fields. The dose to a point is computed as the product of the tissue maximum ratio (TMR), the off center ratio (OCR), and the inverse square factor. The TMR is computed from the measured central axis depth doses for symmetric fields. The OCR is obtained by multiplying the primary OCR (POCR) and the boundary factors (BF's) for the four jaws. The POCR's and BF's were derived from measured beam profiles, which include the effect of off-axis beam quality variations. Using this method, the beam profiles and isodose distributions for asymmetric fields of a 6-MV accelerator were calculated and compared with the measured data. The agreement is within experimental errors both in the penumbra region and along the central ray of the asymmetric field.

A technique for computing dose volume histograms for structure combinations

Graphical displays of three-dimensional dose distribution data are often too complex to be easily assimilated and interpreted for the evaluation of radiation treatment plans. Histograms showing dose versus volume are convenient and useful tools for summarizing dose distribution information throughout the entire volume of a given anatomic structure. They can quickly highlight characteristics such as dose uniformity and hot and cold spots, and can be used to produce statistics including tumor control and normal tissue complication probabilities. To obtain a dose volume histogram for a given structure, it may be necessary to examine its spatial relationships with neighboring structures. They may overlap, be completely disjoint, or one may be contained within another. To resolve potential ambiguities, a procedure has been developed that assigns hierarchies to anatomical structures for the purpose of histogram calculation. The hierarchy assigned to each structure is used to determine the structure within which a given dose matrix point is considered to lie. In this manner, regions of structure intersection are assigned to one object or another, and dose volume histograms can be calculated for each structure separately. From this framework, addition and subtraction of histograms can also be performed. Details of the algorithm are presented along with an example using patient data.

Arbitrary oblique image sections for 3-D radiation treatment planning

Methods for selecting and computing arbitrary image sections for displaying anatomic and isodose information for three-dimensional treatment planning are investigated. Selection of the desired plane may be made by defining a plane that is perpendicular to an existing image section (called the base image) and passing through a line on the base image. Alternatively, the anatomic structures displayed perspectively in three dimensions as a series of contours that can be rotated and translated may be used to define an arbitrary plane for image reconstruction. The viewing screen is considered to be the plane of interest. As a typical three-dimensional image of 30 to 60 sections requires considerable computer storage (on the order of 25 megabytes), a reconstruction algorithm may need extensive memory space or CPU and disk I/O time. Of the schemes examined, we believe the following is the most efficient. One pair of images is read from the disk at a time in sequence and intersections of the rows of the cutting plane with the box formed by the consecutive images are computed. Pixel values of all points between the given images are computed by interpolation. Special cases, such as the cutting plane being parallel to or coincident with an existing image, must be considered separately.

Monte Carlo simulation of a cobalt-60 beam

We have used the Stanford Electron Gamma Shower (EGS) Monte Carlo code to compute photon spectra from an AECL Theratron 780 cobalt-60 unit. Particular attention has been paid to the careful modeling of the geometry and material construction of the cobalt-60 source capsule, source housing, and collimator assembly. From our simulation, we conclude that the observed increase in output of the machine with increasing field size is caused by scattered photons from the primary definer and the adjustable collimator. We have also used the generated photon spectra as input to a pencil beam model to calculate the tissue-air ratios in water and compared it to a model which uses a monochromatic photon energy of 1.25 MeV.

Use of fast Fourier transforms in calculating dose distributions for irregularly shaped fields for three-dimensional treatment planning

In three-dimensional radiation treatment planning, essentially all fields are irregular and compensated. Consequently, it is important to predict accurately dose for such fields to ensure adequate coverage of the target region and sparing of healthy tissues. Traditional approaches, namely, those involving scatter integration and extended source and those utilizing negatively weighted fields, are inaccurate, especially near the boundaries defined by blocks and collimators. In the method presented in this paper, dose distributions for arbitrarily shaped beams are calculated by two-dimensional convolution of the relative primary photon fluence distributions and kernels representing the cross-sectional profiles of a pencil beam at a series of depths. The pencil beam dose distributions are computed, once and for all, with the Monte Carlo method for photon energy spectrum for each treatment machine. The finite size of the source, which is important for cobalt machines, is also taken into account using convolution of the source with the relative primary fluence distribution. Convolutions are performed using fast Fourier transforms on an array processor. Results of calculations are in excellent agreement with measured data. While no data are presented for fields modified by compensators, the method of calculation should apply at least as well for such fields since the variations in fluence distribution for compensated fields are not as sharp as for points near the block boundaries.