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Biomedical subjects

K R Krishnan

Publications and source records attributed to K R Krishnan.

At least 109 records · Page 6Linked to original sources

T-cell predominant balanitis in a traumatic tetraplegic patient: a case report.

T-cell predominant balanitis is described in a 38 year old uncircumcised tetraplegic man whose presenting feature was non-progressive red lesions over the inner prepuce and the glans penis without signs of infection, phimosis, or meatal stenosis. There was no regional lymphadenopathy. He was not exposed to any of the high risk factors for human immunodeficiency virus infection. As the lesion did not respond to topical antibacterial, antifungal, and corticosteroid medications applied in that order, circumcision was performed. Following circumcision, the remaining lesion over the glans penis regressed completely over a period of 1 month. Histopathology of the excised prepuce revealed that both areas of normal nonkeratinizing squamous epithelium as well as areas with hyperplasia. No atypia was noted and Bowenoid changes were not seen. Immunohistochemical studies on the inflammatory infiltrate in the excised prepucial lesion using tissue proliferation markers (PCNA and MIB-1) revealed active proliferation of the band-like infiltrate shown by immunophenotyping (anti-human T cell, CD45RO, clone UCHL1 and L26, pan-B marker) to consist predominantly of T-cells, further supporting the hypothesis of a local immune-mediated inflammatory process as the final pathogenic mechanism of the penile lesion.

Adult↗

A comparison of stereology and segmentation techniques for volumetric measurements of lateral ventricles in magnetic resonance imaging.

Lateral ventricular volumes were measured on magnetic resonance imaging (MRI) scans by independent raters in 18 subjects (11 psychotic patients and 7 healthy control subjects) with two different approaches: a point-counting stereological (PCS) technique and a computerized technique based on segmentation algorithms. The correlation between the two techniques was very high (r = 0.96), and phantom studies showed good validity for both approaches. These findings and the technical simplicity of the PCS technique support its potential use for MRI morphometric measurements.

Cerebral Ventricles↗

Magnetic resonance imaging using deoxyhemoglobin contrast versus positron emission tomography in the assessment of brain function.

1. Function of the brain can be assessed through radiologic imaging to determine physiology of underlying tissue. 2. Until recently, positron emission tomography has been the standard tool with which to study function. 3. In the past few years, several investigators have attempted to use magnetic resonance imaging, which has better resolution and is less expensive, to provide functional information. 4. A noninvasive technique termed BOLD (blood oxygen level dependent) has become a popular area of research to determine physiologic change that occurs in the brain in resting as well as activated states. 5. This article reviews what information PET has given us with regard to function of the brain, followed by a discussion of the principle of functional MRI of the brain with emphasis on what has been done in this field as well as future application of the technique.

Brain↗

Nuclear magnetic resonance spectroscopy: a review of neuropsychiatric applications.

1. Magnetic resonance spectroscopy (MRS) is a powerful new neuropsychiatric research tool which allows for the noninvasive investigation of in vivo biochemistry. This review focuses on the recent applications of MRS to in vivo neuropsychiatric research. 2. The history of MRS as it has progressed from an in vitro method of biochemical analysis to its current in vivo research uses is presented. 3. A brief overview of the physical principles of MRS, including methods for spectral localization, is discussed. 4. Applications of the different MRS modalities (1H, 31P, 19F, 7Li, 13C and 23Na) to various neuropsychiatric disorders such as Alzheimer's disease, schizophrenia, affective disorders, acquired immunodeficiency disease, etc. are reviewed. The study of both fluorinated neuroleptics and the antidepressant fluoxetine using 19F MRS are discussed in greater detail. 5. Finally, potential future neuropsychiatric applications of MRS and specifically 19F MRS are presented.

Animals↗

Arteriosclerotic depression.

Depression is a psychiatric syndrome seen in about 1-2% of elderly patients. When depression is seen for the first time late in life, genetic and psychosocial factors appear to be less important. Structural changes in the brain appear to be more important. In this paper the author presents the concept of arteriosclerotic depression and relates the occurrence of structural changes in the brain to atherosclerosis and the structural changes to the occurrence of depression. Evidence in support of this concept is presented.

Age of Onset↗

Vesical urothelium proliferation in spinal cord injured persons: an immunohistochemical study of PCNA and MIB.1 labelling.

Urinary tract infection occurs more commonly, is more virulent and proves more difficult to eradicate in spinal cord injury persons than in the neurologically intact. In order to find out the peculiarities of the neuropathic bladder which make it vulnerable to recurrent cystitis, we studied the proliferation status of the urothelium in spinal cord injured persons. Eleven consecutive, unselected male spinal cord injury patients (aged 18-73 years) were included in the study. Those with, or undergoing treatment for acute urinary tract infection were excluded. All patients underwent cystoscopy and cold cup bladder biopsy from the trigone and bladder dome. Immunocytochemical analysis was performed using defined, commercially available antibodies for PCNA (PCNA 10, DAKO) and MIB-1 (raised against recombinant DNA defined segment of Ki-67 antigen DAKO) streptavidin/biotin and alkaline phosphatase immunocytochemistry (for MIB-1 with microwave-enhanced antigen retrieval) were used to demonstrate the presence of cell cycling-associated nuclear proteins. Foci of lymphocytic aggregations present in the sections served as in-section controls for antigen preservation. Ten patients showed labelling of 20-70% of cells for PCNA in basal cell layers of dome lining. Higher urothelial layers showed a variable, but generally reduced degree of labelling. Of these 10 patients, three showed complete absence of MIB-1 activity in the basal and other layers of dome urothelium and two demonstrated only a very occasional positive nucleus. MIB-1 labelling was < 5% in four others and it was between 5% and 10% in one.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

Comparative pathology of dome and trigone of urinary bladder mucosa in paraplegics and tetraplegics.

Paraplegic/tetraplegic individuals are prone to develop chronic urinary tract infection, urinary calculi and bladder outlet obstruction, and have a 16 to 28 times higher risk for squamous cell bladder cancer. The preferable method of monitoring those patients who are at high risk of developing vesical neoplasia has been an annual check-up inclusive of cystoscopy and cold cup bladder biopsy of all suspicious areas as well as predetermined random sites. It may be desirable to take a biopsy from one site (when there is no suspicious lesion) with a flexible cystoscope while the patient is sitting in the wheelchair itself in the outpatient clinic instead of multiple biopsies from the done, trigone and both lateral walls of the urinary bladder taken in the operation theatre set-up using a rigid cystoscope with the patient positioned in lithotomy. Before adopting such a cost-saving and more convenient procedure routinely, we evaluated whether any significant additional histopathological findings are obtained by taking bladder biopsies from the dome and the trigone of the urinary bladder instead of just one, be it dome or trigone in the absence of any visible urothelial lesion in the bladder. In forty consecutive tetraplegic/paraplegic patients who did not have any cystoscopically distinguishable urothelial neoplastic lesion such as papilloma, cold cup biopsies of the dome and the trigone were taken randomly before carrying out any diagnostic or therapeutic procedure, eg electrohydraulic lithotripsy of vesical calculi. All the biopsy specimens were evaluated by a pathologist who was unaware of the clinical details and not involved with the primary diagnosis. In 15 cases, significant additional histopathological finding(s) were recorded in the trigone biopsy which were not seen in the dome biopsy (follicular cystitis: n = 4; squamous metaplasia: n = 4; extensive squamous metaplasia with focal atypia: n = 1; limited focal atypia: n = 1; extensive glandular metaplasia: n = 1; intestinal metaplasia and possibly follicular cystitis: n = 1; and follicular cystitis and intestinal metaplasia: n = 1; mild atypia: n = 1; extensive calcification of epithelial denudation: n = 1). Histopathology of dome biopsies revealed significant additional histopathological finding(s) in nine cases (follicular cystitis: n = 2; squamous metaplasia: n = 2; intestinal metaplasia: n = 1; squamous metaplasia and adenomatoid metaplasia and mild atypia: n = 1; features of interstitial cystitis: n = 1; mild dysplasia: n = 1; mild crypt hyperplasia of urothelium with mild atypia: n = 1). Thus in twenty cases (50%), significant additional findings were obtained by taking cold cup random biopsy of the dome as well as the trigone in the absence of any visible morphological changes. Although single site biopsy may be less traumatic, more convenient to the patient as well as to the staff, and cost saving, in the spinal cord injury patients with neuropathic bladder, it may not be diagnostically adequate even in those patients who do not have any cystoscopically distinguishable lesion in the urinary bladder.

Adult↗

Acute hypotension associated with terbutaline nebuliser therapy in a traumatic tetraplegic patient during the spinal shock phase. Case report.

Acute hypotension was observed during the spinal shock stage of a 35-year-old C3 complete tetraplegic patient after receiving nebulised terbutaline for respiratory therapy. Nine weeks later, when he had recovered from spinal shock, he again received nebulised terbutaline but there was no significant fall in arterial blood pressure. This case illustrates the possibility of a serious degree of hypotension occurring in such patients with this drug.

Adult↗

Clinical and phenomenological comparisons of late-onset and early-onset depression.

OBJECTIVE: The authors examined the relationship between age at onset of first depressive episode and clinical features in elderly depressed patients. METHOD: They used data on age at onset and clinical features in 246 elderly depressed patients treated at the National Institute of Mental Health Clinical Research Center for the Study of Depression in Later Life, located at Duke University. RESULTS: Two variables--loss of interest and number of depressive episodes--were related to age at onset in all analyses. CONCLUSIONS: This study confirms the hypothesis that apathy is more prominent in late-onset than in early-onset depression.

Activities of Daily Living↗

Geniculocalcarine hyperintensities on brain magnetic resonance imaging associated with visual hallucinations in the elderly.

Magnetic resonance scans of five geriatric patients presenting with formed visual hallucinations in the absence of other psychopathology were compared with those of 12 healthy elderly subjects for the presence and extent of subcortical and periventricular signal hyperintensity. While the number of discrete brain lesions did not differ between groups, scans from the patient group contained a higher incidence (100% vs. 50%) and greater mean size (11.1 vs. 2.9 mm) of periventricular signal hyperintensity in the posterior region. Peripheral visual acuity was impaired in all of the patients, but cerebrovascular risk factors were not elevated in this group. The authors suggest that structural abnormalities in the area of the primary visual pathway may predispose some older individuals, particularly those with poor peripheral visual acuity, to develop the symptom of visual hallucination.

Aged↗

Ipsilateral subcortical atrophy associated with temporal lobectomy.

Stereologic methods for determining the volume of cerebral structures in vivo via magnetic resonance imaging have identified unilateral hippocampal atrophy among patients with complex partial epilepsy of temporal lobe origin. Metabolic imaging has also identified altered metabolism in temporal as well as extratemporal regions among these patients. As the temporal cortex and subcortical nuclei of the limbic system are reciprocally connected with striatal projection fields, we examined the putamen nuclei for evidence of associated extratemporal volume asymmetry in patients before and after temporal lobectomy. There was no evidence of preoperative putamen volume asymmetry, but a significant postoperative decrement in ipsilateral putamen volume was observed. The magnitude of postsurgical putamen volume asymmetry was correlated with the duration of time since resection. Progressive degeneration of extratemporal projections of the temporal lobe may occur in association with temporal lobectomy.

Adolescent↗

Magnetic resonance imaging in social phobia.

Recent studies have implicated dopamine and the basal ganglia circuits in the pathophysiology of social phobia. Twenty-two patients who met DSM-III-R criteria for social phobia and 22 age- and sex-matched control subjects underwent magnetic resonance imaging (MRI). MRI was performed with a 1.5 Tesla General Electric Signa System. No statistically significant difference was demonstrated between social phobia patients and normal control subjects in respect to total cerebral, caudate, putamen, and thalamic volumes. Although this study failed to demonstrate any specific cerebral structure abnormalities in patients with social phobia, it did reveal an age-related reduction in putamen volumes in patients with social phobia that was greater than that seen in controls. This age-related reduction in putamen volumes in patients with social phobia was not correlated with the severity of their illness.

Adult↗

Brain choline in depression: in vivo detection of potential pharmacodynamic effects of antidepressant therapy using hydrogen localized spectroscopy.

1. Seven subjects with depression and matched controls were studied using proton spectroscopy to test the hypothesis that choline will be elevated in depression. 2. The proton spectroscopy was repeated after recovery from depression. 3. The study confirmed a state dependent increase in choline in the brain. 4. This change may be used as an in vivo marker of change in depression.

Aged↗

Proton spectroscopy of human brain: effects of age and sex.

1. The present study was done to assess the brain metabolites measured by proton magnetic resonance spectroscopy (MRS) in normal individuals. 2. Proton spectroscopy STEAM voxel technique with chemical shift imaging was used to provide localized metabolic information from the brains of 34 normal volunteers (15 males) between the ages of 21 and 75 years. 3. Choline, Creatine and N-acetyl aspartate (NAA) was lower in white matter than gray matter. Choline/NAA and choline/creatine ratios were also lower in white matter. The choline, creatine and NAA were lower in older subjects in the voxel representing cortical and subcortical gray matter. There were no differences between males and females. 4. This preliminary study suggests that age matching is essential for comparative studies of disease states using proton MRS.

Adult↗

Relative accuracy and reproducibility of regional MRI brain volumes for point-counting methods.

Volumetric magnetic resonance imaging (MRI) methods for the measurement of various neuroanatomical regions are of great interest in studies of neuropsychiatric disorders. Both manual and semiautomated methods have been developed. Manual methods include tracing and point counting. Point counting methods are widely used in post-mortem and microscopy studies. Point counting has been well validated for these purposes. In this article, we report in a series of separate studies the accuracy and reproducibility of point-counting methods. Absolute accuracy was evaluated with a spherical phantom. Accuracy and time efficiency were subsequently assessed with an anatomically realistic phantom and various size grids. The point-counting method was also compared to a tracing method. Finally, the reproducibility of the point-counting method for the caudate and putamen was evaluated on four subjects in a test-retest experiment. These studies provide an estimate of the accuracy and time efficiency of point-counting methods. The test-retest reliability was also high for both caudate and putamen. Findings suggest that point counting is a reliable and efficient method for estimating volumes.

Brain↗

Management of pharmacologically induced prolonged penile erection with oral terbutaline in traumatic paraplegics.

Intracavernosal administration of papaverine or prostaglandin E1 for erectile impotence in paraplegics is being practised widely. One of the complications of this therapeutic regimen is prolonged erection which is at present being treated by aspiration of corporeal blood and intracavernosal administration of alpha-adrenergic agonist such as phenylephrine. We report successful management of pharmacologically-induced prolonged erection in three traumatic paraplegics with oral terbutaline therapy. The indications for oral terbutaline therapy were (1) absence of significant coronary artery disease and (2) full erection persisting for more than 2 1/2 h, but less than 4 h duration. The initial dose of terbutaline was 5 mg and the same dose was repeated after 15 min as full erection persisted. Within the next 15 min, penile detumescence was achieved in two paraplegics with papaverine-induced prolonged erection. However, full erection still persisted 15 min after the second dose of terbutaline in the third patient who had received intracavernosal administration of 3.25 micrograms of prostaglandin E1. Therefore, he was given the third and final dose of 5 mg of terbutaline under cardiac monitoring. Penile detumescence was achieved within the next 15 min. It was ensured before administration of the third dose of terbutaline that (1) his blood pressure was within the normal range (for his paralysed status), (2) the heart rate was less than 100 per min and (3) there was no cardiac arrhythmia. Occasional premature ventricular contraction was observed only in the patient who received the third dose of terbutaline, but it was transient, self-limiting and did not warrant any treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗