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Biomedical subjects

J Mohan

Publications and source records attributed to J Mohan.

At least 19 recordsLinked to original sources
PubMed2002

Spectrophotometric determination of serum nitrite and nitrate by copper-cadmium alloy.

A macro and micro assay for the spectrophotometric determination of serum nitrite and nitrate was developed. Nitrite/nitrate in biological samples can be estimated in a single step by this method. The principle of the assay is the reduction of nitrate by copper-cadmium alloy, followed by color development with Griess reagent (sulfanilamide and N-naphthylethylenediamine) in acidic medium. This assay is sensitive to 1 microM nitrate and is suitable for different biological fluids, including sera with a high lipid concentration. The copper-cadmium alloy used in the present method is easy to prepare and can completely reduce nitrate to nitrite in an hour. The present method provides a simple, cost-effective assay for the estimation of stable oxidation products of nitric oxide in biological samples.

Alloys↗
PubMed2001

Chronic atrial fibrillation in patients with rheumatic heart disease: mapping and radiofrequency ablation of flutter circuits seen at initiation after cardioversion.

BACKGROUND: There is little information concerning mapping and radiofrequency ablation (RFA) of arrhythmias seen during reinduction of atrial fibrillation (AF) after pharmacological and/or electrical cardioversion in patients with chronic AF and rheumatic heart disease. METHODS AND RESULTS: Seventeen patients with rheumatic heart disease and symptomatic chronic AF underwent multisite atrial mapping during reinduction of AF after cardioversion. An organized atrial arrhythmia of varying duration was seen to precede the AF in all patients. The earliest atrial activity during this organized rhythm was near the coronary sinus ostium (CS OS) in 14 patients and along the left side of the interatrial septum (IAS) in 3 patients. RFA was performed in 16 patients (14 near the CS OS and 2 along the IAS). Postablation AF was inducible in 1 patient in whom RFA was preformed near the CS OS and in both patients when it was performed along the IAS. At a follow-up of 6 to 56 weeks (mean, 32 weeks), 10 of the 13 patients who had successful ablation were in sinus rhythm. All patients in whom AF was reinducible immediately after RFA continue to be in AF. CONCLUSIONS: Induced AF in patients with rheumatic heart disease begins as a rapid organized arrhythmia with earliest atrial activity near the CS OS in most patients. RFA targeting the region of the CS OS is successful in suppressing the arrhythmia immediately in most of the patients and in most on follow-up.

Adult↗
PubMed2000

A role for phosphorylation of glycogen synthase kinase-3alpha in bovine sperm motility regulation.

The long-term goal of our work is to understand biochemical mechanisms underlying sperm motility and fertility. In a recent study we showed that tyrosine phosphorylation of a 55-kDa protein varied in direct proportion to motility. Tyrosine phosphorylation of the protein was low in immotile compared to motile epididymal sperm. Inhibition or stimulation of motility by high calcium levels or cAMP, respectively, results in a corresponding decrease or increase in tyrosine phosphorylation of the 55-kDa protein. Here we report purification and identification of this motility-associated protein. Soluble extracts from bovine caudal epididymal sperm were subjected to DEAE-cellulose, Affi-Gel blue, and cellulose phosphate chromatography. Tyrosine phosphate immunoreactive fractions contained glycogen synthase kinase-3 (GSK-3) activity, suggesting a possible correspondence between these proteins. This suggestion was verified by Western blot analyses following one-dimensional and two-dimensional gel electrophoresis of the purified protein using monoclonal and affinity-purified polyclonal antibodies against the catalytic amino-terminus and carboxy-terminus regions of GSK-3. Further confirmation of the identity of these proteins came from Western blot analysis using antibodies specific to the tyrosine phosphorylated GSK-3. Using this antibody, we also showed that GSK-3 tyrosine phosphorylation was high in motile compared to immotile sperm. Immunocytochemistry revealed that GSK-3 is present in the flagellum and the anterior portion of the sperm head. These data suggest that GSK-3, regulated by phosphorylation, could be a key element underlying motility initiation in the epididymis and regulation of mature sperm function.

Amino Acid Sequence↗
PubMed1999

Isolation and molecular characterization of AKAP110, a novel, sperm-specific protein kinase A-anchoring protein.

Agents that increase intracellular cAMP are potent stimulators of sperm motility. Anchoring inhibitor peptides, designed to disrupt the interaction of the cAMP-dependent protein kinase A (PKA) with A kinase-anchoring proteins (AKAPs), are potent inhibitors of sperm motility. These data suggest that PKA anchoring is a key biochemical mechanism controlling motility. We now report the isolation, identification, cloning, and characterization of AKAP110, the predominant AKAP detected in sperm lysates. AKAP110 cDNA was isolated and sequenced from mouse, bovine, and human testis libraries. Using truncated mutants, the RII-binding domain was identified. Alignment of the RII-binding domain on AKAP110 to those from other AKAPs reveals that AKAPs contain eight functionally conserved positions within an amphipathic helix structure that are responsible for RII interaction. Northern analysis of eight different tissues detected AKAP110 only in the testis, and in situ hybridization analysis detected AKAP110 only in round spermatids, suggesting that AKAP110 is a protein found only in male germ cells. Sperm cells contain both RI, located primarily in the acrosomal region of the head, and RII, located exclusively in the tail, regulatory subunits of PKA. Immunocytochemical analysis detected AKAP110 in the acrosomal region of the sperm head and along the entire length of the principal piece. These data suggest that AKAP110 shares compartments with both RI and RII isoforms of PKA and may function as a regulator of both motility- and head-associated functions such as capacitation and the acrosome reaction.

A Kinase Anchor Proteins↗
PubMed1998

Peripheral vascular response to mild indirect cooling in patients with homozygous sickle cell (SS) disease and the frequency of painful crisis.

1. In homozygous sickle cell (SS) disease, skin cooling is a common precipitating factor of the painful crisis which is associated with avascular necrosis of active bone marrow. Since skin cooling does not directly induce sickling, we have investigated the nature of the reflex vascular responses to mild cooling in SS patients in a steady state of the disease and compared them with their history of painful crises. 2. Experiments were performed in Jamaica on 60 male SS patients and 30 matched control subjects with normal haemoglobin (AA) genotype. Forearm blood flow (FBF) was measured by venous occlusion plethysmography and mean arterial pressure (MAP) by a Finapres device: forearm vascular resistance (FVR) was calculated as MAP/FBF. Cutaneous erythrocyte flux in forearm and hand was monitored by a laser Doppler meter. The contralateral hand was immersed in cool water at 16 degrees C for 2 min, 6 times, at random intervals of 0.5-3 min. 3. The first cool immersion evoked an increase in MAP, cutaneous vasoconstriction and a net increase in FVR in both AA and SS subjects. However, the direction of change in FVR varied between individuals such that 18 AA subjects showed an increase in FVR (constrictor group) while 12 showed a decrease in FVR, indicating vasodilatation in forearm muscle (dilator group). In contrast, 50 SS subjects showed an increase in FVR and only 10 showed a decrease in FVR. The proportion of subjects who showed net vasoconstriction was significantly greater in the SS than in the AA group (83% versus 60%, P = 0.03, chi 2 test). 4. By the sixth cool stimulus, the 'dilator' group of AA subjects showed no change in FVR while the 'dilator' group of SS patients showed an increase in FVR. We suggest that forearm muscle vasodilatation was the characteristic component of the alerting/defence response to novel or noxious stimuli which habituates on repetition. 5. In the whole group of SS patients, baseline values of cutaneous vascular resistance and FVR increased between stimuli, indicating persistent vasoconstriction, and the sixth cool stimulus still evoked cutaneous vasoconstriction and a net increase in FVR. In contrast, AA subjects showed an increase in baseline FVR between stimuli, but the sixth cool stimulus had no significant effect on cutaneous vascular resistances, or FVR. 6. In SS patients there were no associations between the direction of change in FVR evoked by the first cool stimulus and forearm circumference or skinfold thickness, concentrations of haemoglobin or fetal haemoglobin. However, the frequency of painful crises was significantly greater in the 'constrictor' group than in the 'dilator' group (0.36 versus 0.12/year, P = 0.04, Mann-Whitney test). 7. These results indicate that the primary reflex vasoconstrictor response evoked by mild cooling is stronger and more persistent in SS patients than in AA subjects and is particularly strong in SS patients who are most prone to painful crises. The results are consistent with the hypothesis that skin cooling may precipitate the painful crisis by causing reflex vasoconstriction in muscle, and possibly in bone marrow, so diverting blood flow away from the active marrow.

Acute Disease↗
PubMed1997

Neglected roots of regionalism? The Commissioners for the special areas and grants to hospital services in the 1930s.

The inter-war years in the UK were notable for debates about the extent to which an extension of state intervention in hospital provision was desirable and necessary, and about the limits to and future of the voluntary hospital system which relied largely on various forms of private charity. These themes were intertwined in the UK's 'Special Areas', locations recognized as having suffered adversely from the inter-war depression, with consequent effects on their ability to finance desirable investments in social infrastructures. Grant aid was offered to hospitals in these locations under the terms of the Special Areas legislation of 1934, but there were extensive debates about the principle and practice of such subsidies to hospital development. This paper reviews these debates and considers whether the measures taken by the Commissioners can be seen as neglected antecedents of the regionalism detected in British hospital policy by several commentators.

Economics, Hospital↗
PubMed1996

Diaphyseal aclasis with spinal cord compression. Report of two cases and review of the literature.

In diaphyseal aclasis, the exostoses usually involve long bones, although occasionally the spine is also affected. Very few cases of osteochondroma causing spinal cord compression have been cited. The authors report their experience with two cases of diaphyseal aclasis. In the first case spinal cord compression caused by an exostosis of the lamina of C-2 occurred in a 9-year-old boy; in the second case a large osteochondroma of C-5 occurred in a 45- year-old man. Also included in this report is a review of the literature highlighting the incidence of diaphyseal aclasis, its clinical features and its excellent prognosis in treated cases.

Cervical Vertebrae↗
PubMed1995

Isolation of a spermatozoa motility inhibiting factor from chicken seminal plasma with antibacterial property.

A 78-kDa spermatozoa motility inhibiting factor (SMIF) was purified from chicken (Gallus domesticus) seminal plasma by anion exchange (DE-53) followed by affinity chromatography on concanavalin A-Sepharose. The factor is thermostable and inhibited the spermatozoa motility in a dose dependent manner. In addition, SMIF inhibited the growth of gram negative bacteria, Pasteurella multocida but not gram positive Streptococcus equi. The factor lost its spermatozoa immobilizing property after treatment with trypsin, chymotrypsin or pepsin. The inhibition of SMIF by beta-mercaptoethanol suggest the involvement of disulfide bonds in its activity. Similarly, this property was lost in presence of chicken seminal plasma or incubating SMIF with anti-SMIF antibodies. Evidence is provided for the presence of a high molecular weight protein (> 100 kDa) in chicken seminal plasma that neutralizes the motility inhibiting property of SMIF. No significant decrease in spermatozoa ATP was observed in presence of SMIF suggesting that the loss of spermatozoa motility was due to factors other than depletion in cell's energy. Using anti-SMIF antibodies, a cross-reactive protein was identified in the blood, liver and reproductive tissues of chicken and the seminal plasma of cattle and buffalo. However, the cross-reactive protein failed to inhibit chicken spermatozoa motility. The significance of SMIF in chicken seminal plasma is discussed.

Animals↗
PubMed1995

An outbreak of acute hepatic encephalopathy due to severe aflatoxicosis in Malaysia.

In October 1988, 13 Chinese children died of acute hepatic encephalopathy in the northwestern state of Perak in peninsular Malaysia. The acuteness of the illness differed from previously reported outbreaks described in Kenya, India, and Thailand. Epidemiologic investigations determined that the children had eaten a Chinese noodle, loh see fun, hours before they died. The attack rates among those who had eaten the noodles were significantly higher than those who had not (P < 0.0001). The cases were geographically scattered in six towns in two districts along the route of distribution of the noodle supplied by one factory in Kampar town. Aflatoxins were confirmed in postmortem samples from patients. This outbreak has important public health implications for many developing countries.

Acute Disease↗
PubMed1994

Responses evoked in the forearm vasculature on normal human subjects on repetition of mild, indirect cooling.

We have studied responses evoked in the forearm vasculature of normal subjects by mild cooling of the contralateral hand; it was transferred from thermoneutral water at -33 degrees C to water at 16 degrees C for 2 min. Total forearm blood flow was measured by venous occlusion plethysmography, cutaneous red cell flux was monitored with a laser Doppler flowmeter and arterial pressure was recorded by semi-automatic sphygmomanometry. In each of two groups (I and II) of twelve and 15 subjects, mild cooling evoked a rise in mean arterial pressure, but in each group, approximately half (six and eight respectively) showed a decrease in total forearm vascular resistance (FVR) in response to the first cool immersion (dilator group), while the remainder showed an increase in FVR (constrictor group), apart from one of group II who showed no change in FVR. Cutaneous vascular resistance tended to increase in both the dilator and constrictor groups, but this did not reach statistical significance. When cooling was repeated six times in group II, the decrease in FVR (-18% from control) in the dilator group reversed to an increase in FVR (+25%) by the sixth immersion, while the increase in FVR (+55%) in the constrictor group persisted through to the sixth immersion (+23%). We propose that mild cooling evokes a primary reflex vasoconstrictor response in forearm muscles, but that this can be overcome in some subjects by the characteristic muscle vasodilatation of the alerting response which is evoked by novel, or noxious stimuli; the latter is known to habituate on repetition of the stimulus.

Adult↗
PubMed1994

A comparative study in subjects with homozygous sickle cell disease and in normal subjects of responses evoked in forearm vasculature by mild, indirect cooling.

We have studied responses evoked in the forearm vasculature of twelve subjects with homozygous sickle cell disease (SS) and in eight dark-skinned controls of West Indian ancestry (AA) by mild cooling of the contralateral hand in water at 16 degrees C for 2 min; this stimulus was repeated six times at randomized time intervals. Total forearm blood flow was measured by venous occlusion plethysmography, cutaneous red cell flux was monitored by a laser Doppler flowmeter and arterial pressure was recorded by semi-automatic sphygmomanometry. Of the AA subjects, three showed a decrease in total forearm vascular resistance (FVR, of -10%) in response to the first immersion and this reversed to an increase in FVR (+7%) by the sixth immersion. The remaining five showed an increase in FVR (+65%) which persisted until the sixth immersion (26%). By contrast, all SS subjects showed an increase in FVR (+32%) which persisted to the sixth stimulus (+27%). Further, on a scale of discomfort of 0-10, none of the AA subjects rated the cool stimulus higher than 0, whereas SS subjects gave a rating of 7 for the first stimulus which decreased to 5 by the sixth stimulus. Both AA and SS subjects showed an increase in arterial pressure and a tendency towards vasoconstriction in forearm skin. We propose that, as in Caucasian AA subjects, dark-skinned AA subjects showed a primary reflex vasoconstriction in forearm muscle in response to mild, indirect cooling which was overcome in some individuals by muscle vasodilation of the alerting response that is evoked by novel or noxious stimuli.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Coronary heart disease: trends in spatial inequalities and implications for health care planning in England.

The idea of health gain has recently received particular emphasis in health policy in England. One of the areas where there is considerable scope for health gain is in the reduction of mortality due to Coronary Heart Disease. Some reduction in mortality rates due to this cause have already been achieved in England in the 1980s. However, the change in standardised mortality rates varies around the country. A review of studies of geographies of declining CHD mortality shows that such geographical variation is typical of other countries which have recently experienced a reduction in the CHD epidemic. The paper presents the results of an analysis of change in spatial inequality in coronary heart disease mortality among the population aged 35-74 for the 190 District Health Authorities in England over the period 1982-1989. Data were derived from counts of cause-specific deaths and population estimates published by the Office of Population Censuses and Surveys. Various approaches were used to assess the change in spatial disparity which has accompanied the average overall reduction in mortality rates over the study period. The results show that the trends vary between age and sex groups in the population and that, particularly for older people, overall health gain across the country is being achieved at the cost of greater inequality in health between areas. The implications for local health strategies with respect to coronary heart disease reduction are discussed.

Adult↗
PubMed1993

Angiotensin converting enzyme activity in female reproductive tract of domestic fowl (Gallus domesticus) and its interactions with semen.

Presence of angiotensin converting enzyme (ACE, EC 3.4.15.1) in female reproductive tract and its interaction with semen has been investigated in domestic fowl. Higher activity of ACE was detected in homogenates of infundibulum region followed by magnum and relatively low level was noticed in rest of the parts of the oviduct (i.e. isthmus, uterus, uterovaginal-junction and vagina). This decreasing order in ACE activity was, however, reversed when these segments were incubated with semen. ACE in the ovarian follicular wall increased with corresponding increase in the follicle size. Presence of some stimulatory or inhibitory substances for ACE in the oviduct of fowl is suggested.

Animals↗
PubMed1992

Effects of cadmium salt on phosphomonoesterases activity and fertilizing ability of fowl spermatozoa.

Daily administration of cadmium salt for 25 days (2.5 mg per Kg body weight) in the male domestic fowl caused the end of treatment period. An increased incidences of concentration. Fertility dropped to zero at the end of the treatment period. Activity of acid and alkaline phosphomonoesterases were also drastically reduced by the end of treatment period. An increased incidences of morphological abnormalities of spermatozoa were noticed in the treated birds. After 46 days cessation of the treatment, full recovery of the above measures was found. These alterations suggest the reversible type of effect of cadmium chloride on the spermatozoa of male domestic fowl.

Animals↗
PubMed1991

Histamine in egg yolk: heat resistance and relation to production status.

1. The presence of histamine in egg yolk, its losses during storage, incubation and heating, and its relationship to cage density stress and the egg production status of hens are described. 2. A significant (P less than 0.05) reduction in the histamine concentration of egg yolk was noted after incubating or heating egg yolks or on storage eggs. 3. Histamine concentration was greater in the yolks of high egg producing hens. 4. The concentrations of histamine in egg yolks did not change significantly (P less than 0.05) on keeping the hens individually in a cage, pairing them in the same size cage or after separating them again to individual cages.

Animals↗