Genetics of mental retardation.

Mental retardation can follow any of the biological, environmental and psychological events that are capable of producing deficits in cognitive functions. Recent advances in molecular genetic techniques have enabled us to understand more about the molecular basis of several genetic syndromes associated with mental retardation. In contrast, where there is no discrete cause, the interplay of genetic and environmental influences remains poorly understood. This article presents a critical review of literature on genetics of mental retardation.

Corneal ulcer caused by Nocardia asteroides in a patient with leprosy.

Nocardia asteroides is a rare cause of keratitis usually associated with trauma. We report a case of corneal ulceration caused by N. asteroides in a patient with leprosy. This is the first case report of nocardial keratitis from Southeast Asia. The diminished corneal sensation in a patient with leprosy could be a predisposing factor for development or exacerbation of corneal ulceration.

Assessing outcomes for dysphonic patients.

This study was designed to evaluate a disease-specific outcome measure for patients with selected voice disorders and to relate this instrument to a standardized quality of life measurement. In addition, the study attempts to document the degree of handicap for dysphonia patients globally, between different vocal pathologies, and in comparison to other chronic diseases. In this prospective, observational study, 260 adult patients evaluated for alterations of voice completed a general quality of life measure (the Medical Outcomes Trust Short Form 36-Item[SF-36]) and a voice-specific instrument (Voice Handicap Index [VHI]) pretreatment. The highest correlation was between the social functioning score of the SF-36 and the total score of the VHI and the physical, emotional, and functional subscales (p < 0.001) of the VHI. Significant correlation was also obtained for the SF-36 domains mental health (p < 0.01), general health (p < 0.01), and role functioning emotional (p < 0.017) with the three VHI domains and the total VHI score. Patients had significantly lower scores than the general U.S. population in five of the eight domains of SF-36. Patients with vocal fold paralysis had the highest level of pretreatment disability as measured on both the VHI and SF-36 among voice patients. The patients with dysphonia had a lower level of physical functioning than the patients with chronic sinusitis (p < 0.01), reflecting a greater handicap. In addition, the dysphonia group had lower levels of social functioning than the angina (p < 0.01) and sciatica (p < 0.01) groups and a lower score for mental health than the angina group (p < 0.01). The SF-36 correlates with the VHI in the domains of social functioning, mental health, and role functioning emotional. The baseline handicap for voice disorders represents a significant disability even in comparison to conditions such as angina pectoris, sciatica, and chronic sinusitis.

Psychosocial aspects of seropositive HIV patients.

Acquired immunodeficiency syndrome, has become a serious global health problem with an enormous biomedical impact and diverse psychological and clinical manifestation. A study was conducted wherein seropositive HIV patients admitted in a medical ward were assessed for demographic profile, presenting physical illness, mode of contacting the infection, psychiatric morbidity and associated psychosocial factors. The results revealed male preponderance and heterosexual unprotected exposure as the common mode of contacting the illness. It was observed that majority of the patients presented with tuberculosis. Psychiatric assessment revealed a high rate of depressive and anxiety syndromes. Thus it was concluded that the HIV-infected population has a higher prevalence of psychiatric disorders as compared to the general population. The reason for this includes psychological, biological and social factors.

Blocked field effects on collimator scatter factors.

In routine dosimetry we assume separability of the collimator (Sc) and phantom (Sp) scatter components that together comprise the total scatter factor (Sc,p). In practice, the addition of blocking also affects the photon fluence attributable to the treatment head and flattening filter in a complicated way. The reduced aperture blocks out some of the head scatter contribution, while the block and tray add back secondary scatter. In the following we present techniques for directly measuring the aperture effect on Sc in air or in a full-scatter phantom. The change in Sc is found to be a scaleable quantity that can be modelled as a simple linear fit to the ratio of projected open-to-blocked equivalent square fields. Measurements have been made for 6, 18 and 24 MV photon beams on one Varian 2500 and two Varian 2100c accelerators. Results indicate a progressive loss of collimator scatter contribution with increased field blocking that is amplified with increasing energy. Block and tray scatter only contribute significantly to Sc for large fields and treatment distances of 80 cm or less. Application of these corrections in monitor unit calculations is presented.

Transport phenomena in laminar flow of blood.

Recently it has been shown experimentally that transport of heat and gas (specifically oxygen and helium) are augmented in the laminar flow of aqueous suspensions of polystyrene spheres 50 and 150 micrometer in diameter. In this report, data on heat and gas transport are correlated. Application of this correlation to flowing blood leads to the following conclucions. There is no significant augmentation of oxygen and heat transport in flowing blood even at shear rates much higher than physiological shear rates; an observation which is in accord with the experimental results. The augmentation of the diffusion coefficient of plasma proteins in flowing blood, though not very high, appears to be measurable. Of the total measured augmentation of about 6000--30 000% in platelet diffusivity in flowing blood, quoted from the literature, about 500% is attributable from this correlation to fluid mechanical forces, and the balance is hypothetically attributed to other forces (electrical or biochemical) present in blood.

Thermal design of a heat exchanger for heating or cooling blood.

Experimental data, and their correlation with predictions from theory, are presented for the thermal design of a countercurrent heat exchanger for heating or cooling blood. The thermal design considers the influence on the Nusselt number of blood and the heat exchanger effectiveness of variables such as the blood flow rate, tube diameter and length, and the thermal properties of blood. The data presented are compared with data from the literature and with predictions from theory. Insofar as the design of a blood heat exchanger is concerned, flowing blood can be considered a single-phase fluid. Results of the thermal design analysis are applicable to attempts to produce and control blood hyperthermia for applications such as the perfusion of tumours of the extremities, and to efforts to induce hypothermia during open-heart surgery.

Thermal conductivity and diffusivity of neuroblastoma tumor.

In the application of hyperthermia to cancer management, it would be useful to know the temperature/tim profile of heated tissues, including the tumor and surrounding normal structures. To obtain this information, knowledge of thermal conductivity and diffusivity of the tissues is required. The thermal conductivity of neuroblastoma was determined by a transient technique to be 89% of the thermal conductivity of water at 25 degrees, 37 degrees, and 44 degrees C. From the latter measurements, the thermal diffusivity of neuroblastoma cells was estimated as 93% of the thermal diffusivity for water. Further, in this study of neuroblastoma cells, the water content was measured as 87.4 g/100 ml of cells, a rather high value not atypical of tumor cells. From literature values of density, specific heat, and thermal conductivity, values for the thermal diffusivity of a variety of normal tissues were estimated. The thermal diffusivity values of normal tissues and neuroblastoma cells exhibit an excellent correlation with water content.

Limitations of diagnostic value of the sweat test.

The sweat test, even if carried out by an experienced technician, sometimes lacks reproducibility owing presumably to physiological variations (patient's diet, temperature, and other factors at present unrecognized). Some patients are particularly prone to exhibit this variability and in them a single sweat test is almost valueless. The aldosterone status is believed to be responsible for a reciprocal relationship between sweat sodium and potassium concentrations: tests done on 8 patients show that a high sweat potassium is associated with a correspondingly lower sodium--a circumstance which must be borne in mind when interpreting a patient's sweat sodium. Of 30 patients presenting with a variety of symptoms compatible with a diagnosis of cystic fibrosis and with sweat sodium ranging from 50 to 75 mEq/1 (50-75 mmol/1), only 4 have proved to have cystic fibrosis after several years of observations; 13 have later been diagnosed as having asthma. The problem of the 'grey area' of uncertainty is aggravated by the heterozygous state which is also associated with a sweat sodium in this range. Repeated sweat tests are indicated if the sweat sodium lies within the 'grey area', and the diagnostic importance accorded the test should diminish as the sodium value approaches this area. The diagnosis of cystic fibrosis must remain in doubt unless there is strong supportive clinical evidence.