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Biomedical subjects

N Nath

Publications and source records attributed to N Nath.

At least 91 records · Page 5Linked to original sources
PubMed1981

Comparative evaluation of radioimmunoassay kits used for testing blood for hepatitis B surface antigen.

A comparative evaluation of six licensed radioimmunoassay kits for the detection of hepatitis B surface antigen (HBsAg) has been performed. Each method met the federal licensure requirements for the test. The performance of the kits varied considerably, however, when they were challenged to the limits of their sensitivities. During the period December 1978 through March 1979, four kits were judged to be of equivalent high sensitivity, whereas two were less sensitive. Three of the kits, including two of those with high sensitivity, generated a high (6%--7%) proportion of false reactive results. The sensitivities of all kits decreased during the shelf lives of the reagents.

Evaluation Studies as Topic↗
PubMed1981

Hepatitis B virus (HBV) infection among children and adults in the Solomon Islands.

A total of 593 inhabitants of Graciosa Bay, Santa Cruz, the Solomon Islands were tested for HBsAg and anti-HBs in 1974 and again in 1977. An additional 102 children born during this study period were tested for HBsAg and anti-HBs in 1977. Loss of HBsAg was observed in 20% of the 66 HBsAg-positive individuals identified in 1974 and retested in 1977. Conversely, acquisition of HBV infection, as documented by seroconversion on HBsAg or anti-HBs, was observed in 38% of the individuals identified as negative for all HBV markers in 1974. Acquisition of HBsAg was noted in 22 individuals, eight of whom were born after 1974. Acquisition of HBsAg was noted in 66 individuals, two of whom were born after 1974. Males and females acquired HBV infection at somewhat similar rates (42% vs. 34%), except between ages 15 and 29 years, when males were infected at a much higher rate (53%) than females (11%) (p = 0.008). Contact with a carrier appears to be the predominant mode of transmission of the virus. Acquisition of HBV by children and females was strongly correlated with the presence of an HBsAg-positive individual among the household contacts. Adult males, on the other hand, tended to acquire HBV infections from sources outside their family or household setting. The relationship between the patterns of acquisition of HBV infection and the cultural practices in this Melanesian population is discussed.

Adolescent↗
PubMed1980

Distribution of hepatitis B e antigen (HBeAg) and anti-HBe in carriers with different levels of HBsAg.

Blood samples from 154 asymptomatic carriers of HBsAg were studied for the presence of HbeAg and anti-HBe using techniques of rheophoresis and a micro solid phase radioimmunoassay (micro-SPRIA). The level of HBsAg in each sample was determined by titration using reverse passive hemagglutination (RPHA) test. The significance of relationship between the titer of HBsAg, HBeAg, anti-HBe, and anti-HBc were statistically analyzed. Micro-SPRIA detected almost twice as many reactives for HBeAg and anti-HBe as were found by rheophoresis; the difference in sensitivity was significant (P less than 0.001). The mean HBsAg titer of 41 samples reactive for HBeAg was 11,181, while it was 3,032 for 92 samples reactive for anti-HBe. The remaining 23 samples with no detectable HBeAg or anti-HBe had a mean HBsAg titer of 1,018. The differences in the distribution of HBsAg among the three categories is statistically significant (P less than 0.005). HBeAg was most likely to be found in samples with higher concentrations of HBsAg.

Antibodies, Viral↗
PubMed1980

Hepatitis-associated markers in the American Red Cross volunteer blood donor population. I. Trends in HBsAg detection, 1975--1978.

From January 1975 to December 1978, 19,140,169 units of blood were collected by the American Red Cross at 57 regional locations. Each unit was tested for hepatitis B surface antigen (HBsAg) by a single commercial radioimmunoassay test system. A total of 15,954 donations were reported reactive, representing a rate of HBsAg reactivity of 0.83/1,000 units tested. The rate during 1975 was 0.94/1,000 units tested, decreasing to 0.71/1,000 units tested in 1978 (p < 0.005). The prevalence of HBsAg among first-time donors was 2.08/1,000 during 1977 and 1978, 2.7 times higher than that calculated for repeat donors (0.77/1,000 donors). Substantial geographic variation in the prevalence and rate of detection of HBsAg was observed.

Blood Donors↗
PubMed1980

Hepatitis-associated markers in the American Red Cross volunteer blood donor population. ii. Distribution of level of HBsAg reactivity by radioimmunoassay and occurrence of nonspecific reactivity.

During the year 1978 this laboratory evaluated the specificity of all samples found reactive for hepatitis B surface antigen (HBsAg) by 44 of 57 regions of the American Red Cross Blood Services. Radioimmunoassay detected a total of 1.921 HBsAg-reactive sampled among more than three million donor units tested. A vast majority (96%) of the samples had high level of HBsAg (greater than or equal to 20 ng/ml). Only about 50% of the samples with low level of HBsAg (less than 20 ng/ml) were reactive in reversed passive hemagglutination. There were 13 samples that were repeatable for HBsAg but were considered nonspecific as they were nonneutralizable in radioimmunoassay, 2 donors who showed nonspecific reactivity were further tested and it was found that the reactivity in radioimmunoassay persisted for more than 9 months, and this reactivity was also detectable by a second commercial kit for HBsAg. Antibodies to core and surface antigen were not found in any of the nine samples that were tested. The explanation of this nonspecific reactivity is unclear, but the data suggest that the nonspecific factor(s) may be an inherent property of the sample rather than a deficiency of the test reagents.

Antibody Specificity↗
PubMed1980

Hepatitis-associated with markers in the American Red Cross volunteer blood donor population. III. Influence of donor selection practice upon HBsAg prevalence.

The American Red Cross collects blood from a number of defined subsets of the donor population and teh proportion of blood collected from each subset varies widely from center to center. A large part of the variation in prevalence of HBsAg may be related to variations in the proportion of blood collected from plants and factories, military units and schools or colleges. We have derived a regression equation, significant at the p less than 0.001 level, which links HBsAg prevalence with these collection parameters. Using this equation, we were able to predict the prevelance of HBsAg among first-time donors in 6 of the 9 geographic divisions of the United States with an accuracy exceeding 10%. The predictions for the remaining division were within 35% of the actual value. Correlation studies were supported by measurements of true donor prevalence in three blood centers.

Blood Donors↗
PubMed1980

Time-course of changes of liver tryptophan pyrrolase (tryptophan oxygenase) and liver and kidney glucose-6-phosphatase in rats shifted from high- to zero-protein diets.

Time-courses of changes in the activities of liver and kidney glucose-6-phosphatase [EC 3.1.3.9] and hepatic tryptophan pyrrolase [EC 1.13.1.12; TPO] in rats pre-fed high-protein diets for 5 days and then shifted to zero-protein diets were studied. Liver glucose-6-phosphatase activity decreased 1 day after the dietary shift but then increased and remained significantly higher than the 0 day value for the next 2 days. Changes in liver glycogen were found to be intimately and inversely related to liver glucose-6-phosphatase activity. Changes in kidney glucose-6-phosphatase activity paralleled the pattern of changes observed in liver activity. An initial decrease in TPO activity was followed by increased enzyme activity up to the 3rd day of the dietary shift. Later there was a rapid fall in tryptophan pyrrolase activity. Changes observed in these specific enzyme proteins differed from those observed in total tissue proteins. Alterations in the activities of these enzymes and changes in other parameters are compared with those observed earlier with the reverse type of dietary shift.

Animals↗
PubMed1980

Distribution and activity of esterases in the enteric epithelial cells of certain lepidopteran pests during metamorphosis.

Esterases have been investigated in the enteric epithelial cells of the larva, pupae of varying ages and adult of four Lepidopteran moths--Achoe janata, Atteva fabricella, Hypsa alciforon and Paralellia algira. The foregut epithelium of the larvae, pupas and adults showed negative results for esterases. Positive sites of esterases activity were found in the peripheral region of epithelial cell of the larval midgut: the apical region being free of enzymatic activity. Escape of the enzyme from the cells into the lumen of the midgut was not observed in any of the moths presently investigated. Anterior proctodaeal epithelial cells show appreciable enzymatic activity, while those of posterior hindgut exhibit negative reaction. In prepupal stage the regenerative cells of the midgut epithelium do not show activity of the enzyme at both the apical and peripheral ends. Esterases appear in the regenerative cells after the 2. day of pupal period and thereafter positive results throughout the period of metamorphosis. Activity of the enzyme increases in the midgut digestive cells of newly emerged adult. However in the cells of hindgut epithelium there is no change in the esterases activity or localisation during metamorphosis. The following conclusions have been drawn: 1. Hydrolases investigated are esterases (not lipases) which are present in the enteric epithelium of moths. 2. With the change in the metabolic rate during metamorphosis of insects esterase activity is reduced in epithelial cells at the onset of pupal period, while in pharate as well as newly-emerged adult the enzyme activity increases.

Animals↗
PubMed1979

A new antigenic determinant on HBsAg. Geographic and subtype distribution and association with HBeAg and anti-HBe.

A new antigenic specificity for HBsAg is described, and its usefulness as an epidemiological marker is discussed. This specificity, l, was found in specimens from all geographic areas studied (United States, Latin America, South Africa, the Solomon Islands, and New Guinea). In these areas, l was strongly associated with HBsAg/ay; y-positive, l-negative samples were observed only among specimens from United States volunteer blood donors. This determinant allowed a distinction of HBsAg/ad classes. Thus, the l determinant was detected in 51.4% of HBsAg/adw4, 44.1% of HBsAg/adw(non-w4), and 50% of HBsAg/adr. The association of l and other HBsAg determinants with HBeAg or anti-HBe was also investigated. HBeAg was found to be associated with the presence of the l determinant and with the r determinant. Anti-HBe was associated with the presence of the d and w determinants and with the absence of the l specificity.

Antibodies, Viral↗
PubMed1978

A highly sensitive radioimmunoassay technique for subtyping the antibody to hepatitis B surface antigen.

A highly sensitive technique for determining the subtype specificity of antibody to hepatitis B surface antigen (anti-HBs) is described. Immunoadsorbent consisting of controlled pore glass coated with subtype specific HBsAg was used to remove homologous antibody from the test samples before testing them for residual antibody by a commercially available radioimmunoassay (RIA). A total of 73 anti-HBs-positive samples from asymptomatic blood donors were tested. In nearly 80% of these samples the subtype reactivity could be determined by this technique. Only 67% could be typed by conventional liquid phase absorption RIA and 22% by passive hemagglutination inhibition techniques. Among the samples with low anti-HBs titer, ad and ay subtypes were found with equal frequency; however, with the increase in anti-HBs titer, considerably higher proportion of ad specificity was detected.

Antibodies, Viral↗
PubMed1978

Relationship of subtypes of hepatitis B surface antigen with e antigen and its corresponding antibody.

A total of 3,212 samples of blood from asymptomatic volunteer donors positive for hepatitis B surface antigen (HBsAg) by radioimmunoassay and 860 samples negative for HBsAg were tested for the presence of hepatitis e antigen (HBeAg) and its corresponding antibody (anti-HBe) using a rheophoresis technique. Neither HBeAg nor anti-HBe was detected in any sample negative for HBsAg. Of the HBsAg-positive samples, 237 (7.4%) contained HBeAg and 749 (23.3%) had anti-HBe. HBeAg was significantly (P less than or equal to 0.0005) more likely to be in samples with high titers of HBsAg. Anti-HBe had an equal chance of occurring in samples with low or high titers of HBsAg. Both HBeAg and anti-HBe were found in samples with HBsAg subtypes ad or ay. However, a significant association (P less than or equal to 0.0005) between HBsAg/ay and HBeAg as well as an association between anti-HBe and HBsAg/ad was found.

Antibodies, Viral↗
PubMed1978

Type B hepatitis after needle-stick exposure: prevention with hepatitis B immune globulin. Final report of the Veterans Administration Cooperative Study.

Hepatitis B immune globulin (HBIG) and immune serum globulin (ISG) were examined in a randomized, double-blind trial to assess their relative efficacies in preventing type B hepatitis after needle-stick exposure to hepatitis B surface antigen (HBsAG)-positive donors. Clinical hepatitis developed in 1.4% of HBIG and in 5.9% of ISG recipients (P = 0.016), and seroconversion (anti-HBs) occurred in 5.6% and 20.7% of them respectively (P less than 0.001). Mild and transient side-effects were noted in 3.0% of ISG and in 3.2% of HBIG recipients. Available donor sera were examined for DNA polymerase (DNAP) and e antigen and antibody (HBeAg; anti-HBE). Both DNAP and HBeAg showed a highly statistically significant correlation with the infectivity of HBsAg-positive donors. Hepatitis B immune globulin remained significantly superior to ISG in preventing type B hepatitis even when the analysis was confined to these two high-risk subgroups. The efficacy of ISG in preventing type B hepatitis cannot be ascertained because a true placebo group was not included.

Adolescent↗