Search PubMed⌕ Search

Biomedical subjects

H Stern

Publications and source records attributed to H Stern.

At least 127 records · Page 7Linked to original sources
PubMed1984

Replication and nicking of zygotene DNA sequences. Control by a meiosis-specific protein.

A protein having a molecular weight of 73,000 daltons has been purified from the nuclear membranes of preleptotene, leptotene, and zygotene cells. It has been named the leptotene protein (L-protein) because of its role in suppressing the replication of zygotene DNA sequences through leptotene until the initiation of zygotene DNA synthesis. The protein has been found to be highly specific in its inhibitory activity. S-phase replication in somatic nuclei and in microspore nuclei are unaffected by the protein. Only zygotene DNA sequences appear to be affected. L-protein binds specifically to zygotene DNA. The binding is limited to a relatively short DNA segment, probably no longer than 90 base pairs (bp). Chloroplast and mitochondrial DNA do not bind to the protein, but a low level of binding is displayed by DNA from several other eukaryotic species. The L-protein also has the capacity to nick the bound DNA in the presence of ATP. Nicking does not occur in the absence of binding. Using supercoiled plasmids with zygotene DNA inserts as substrates, the nicking has been found to be confined to a small region of the plasmid and to occur in only one of the strands. The L-protein is considered to be one of the principal factors responsible for the irreversible commitment of cells to meiosis at the end of the preleptotene S-phase. It is also proposed that its endonucleolytic activity plays a role in the initiation of synapsis.

Cell Cycle Proteins↗
PubMed1984

Pharmacodynamic effects of ouabain following single sublingual and intravenous doses in normal subjects.

In this intraindividual, placebo-controlled, double blind study the dynamic effects of single doses of ouabain 0.5 mg i.v. and 12 mg sublingual were compared with those of the vasodilator sublingual nitroglycerin 0.8 mg. In 12 (sublingual) and 6 (i.v.) healthy volunteers, respectively, cardiac performance was assessed for 60 min after administration, using systolic time intervals ( QS2c , PEPc, PEP/LVET), electrical impedance cardiography ( (dZ/dt)/RZ index) and echocardiography (EDD, ESD, FS). After i.v. ouabain the typical positive inotropic glycoside effects appeared (shortening of QS2c , PEPc, and PEP/LVET, increase of (dZ/dt)/RZ and FS, decrease of EDD and ESD). With nitroglycerin preload reduction diminished cardiac performance, as shown by a rise in PEPc and PEP/LVET and depression of (dZ/dt)/RZ. In addition, EDD (not significant) and ESD were somewhat reduced, FS was enhanced, and QS2c tended to shorten. Following sublingual ouabain, QS2c was unchanged, there was an increase in PEPc and PEP/LVET, a decrease in (dZ/dt)/RZ and FS, EDD was unchanged, and ESD rose. By this route the absolute magnitude of the effects was about 1/3 that of the i.v. drug action. The spectrum of effects of sublingual ouabain indicates a reduction in cardiac performance without any detectable inotropic action. The effects seem to be induced by load changes, with an indication of an increase in afterload although an additional preload reduction cannot be excluded. This dose of the drug given by the sublingual route appears, therefore, to alter cardiac function via an effect on the peripheral circulation, although the final mechanism has not yet been elucidated.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1984

Chromosome organization in the regulation of meiotic prophase.

The prophase stages of meiosis, particularly zygotene and pachytene, are organized to sustain the events required for recombination between homologous chromosomes. Three categories of DNA sequences are believed to function in the control of these events. One category comprises the sites of transcription for meiosis-specific proteins. The other two categories are related to the structural organization of chromosomes at meiotic prophase. Sequences that are delayed in replication until zygotene may provide the sites for chromosome alignment in securing the synapsis of homologues. General chromosome synapsis is presumed to be functionally distinct from the synapsis of DNA strands that occurs in localized regions at which recombination may take place. Recombinational synapsis probably involves families of moderately repeated sequences, here designated as PDNA. PDNA segments have a compound organization. Each of their ends is occupied by a moderately repeated sequence that belongs to one of several hundred families designated as 'PsnDNA'. The latter range from 150-300 bp in length and do not hybridize with the internal PDNA regions. PsnDNA sequences are the sites at which most of the programmed nicking, gapping and repair syntheses occur during pachytene. They are also the sites at which histones are displaced by a meiotic prophase-specific protein that somehow renders the PsnDNA accessible to the action of meiotic endonuclease. This structural change in the chromatin is partly controlled by a meiosis-specific small nuclear RNA (PsnRNA) that is homologous with PsnDNA and also has a specific affinity for the histone-replacing protein. The complex of events associated with the transformation in PsnDNA chromatin regions is also subject to control by homologous chromosome pairing.

Base Sequence↗
PubMed1983

Indirect enzyme-linked immunosorbent assay (ELISA) for detection of IgG antibodies against Coxsackie B viruses.

In tests for IgG antibodies against Coxsackie B viruses in man, the enzyme-linked immunosorbent assay (ELISA) was essentially group-specific and, unlike the type-specific neutralisation test, usually failed to detect rises in antibody titre in paired, acute and convalescent, sera. However, in rabbits immunised against Coxsackie B viruses, ELISA demonstrated both group- and type-specific antibody responses. The lack of type-specificity of ELISA in man is probably because repeated infection with enteroviruses--echoviruses and Coxsackie A as well as Coxsackie B--results in masking of the type-specific antibody response by group-specific antibody.

Adult↗
PubMed1982

Comparison of enzyme-linked immunosorbent assay, radioimmunoassay, complement fixation, anticomplement immunofluorescence and passive haemagglutination techniques for detecting cytomegalovirus IgG antibody.

The radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) techniques were found to be comparable in sensitivity and specificity for detecting cytomegalovirus IgG antibody, and 10 to 100 times more sensitive than complement-fixation (CF), anticomplement immunofluorescence (ACIF) and passive haemagglutination (PHA). In screening tests for antibody, the frequency of false-positive and -negative results was 0.6% for RIA and ELISA, 1.5% for CF, 1.6% for ACIF and 3.6% for PHA. PHA was the least satisfactory test, largely because of technical problems. Cytomegalovirus (CMV) infection is an important cause of congenital brain damage and is also a major complication of both prolonged immunosuppressive therapy, especially in patients with organ transplants, and multi-donor blood transfusions. For serological diagnosis of infection, as well as for screening for antibody in patients and in blood donors, the solid-phase indirect radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) techniques offer distinct improvements in sensitivity over previous methods. Although the principle of both tests, based on the detection of antigen-antibody reactions by means of a labelled anti-antibody, is the same, each possesses its own particular technical advantages and disadvantages, and both require their own expensive equipment for the reading of the results. There is still a lack of data on how they compare in sensitivity and specificity. The present study was undertaken to compare the two methods for the detection of CMV IgG and to evaluate them against the older techniques of complement-fixation (CF), passive haemagglutination (PHA) and anticomplement immunofluorescence (ACIF).

Antibodies, Viral↗
PubMed1982

Employment training for disadvantaged or dependent populations.

The vocational rehabilitation process is viewed as having two dominant work-related components: the actual work-training experience and employability skills. The paper argues that both components are critical and must be integrated. The major role of the vocational rehabilitation agency is viewed as that of provider of employability (or job-seeking) skills programs. These programs consist of: (1) employability skills courses, (2) work performance demand standard setting, and (3) on-the-job rotational task schemes. Actual work skills can only be provided in the "real world" of work. Centralized work-training programs are viewed as creating inappropriate socialization and only moderately transferable skills.

Employment↗
PubMed1981

Non-A, non-B hepatitis in West London.

Acute and convalescent sera from 368 patients drawn from a 3-year survey of viral hepatitis in West London were tested for radioimmunoassay for evidence of recent infection with hepatitis A or B and, if neither was found, antibody to Epstein-Barr (EB) virus and cytomegalovirus. In 215 patients (58%) there was evidence of hepatitis A, in 98 (27%) hepatitis B, and in 5 both A and B. 2 patients with evidence of recent EB virus infection were excluded, leaving 48 (13%) attributed to non-A, non-B hepatitis. This illness was milder than hepatitis B as judged by duration of jaundice and peak serum bilirubin alanine-aminotransferase levels. The ratio of men to women was 1.4 to 1, but there was an excess of women in their twenties, most of whom were single. Only one had received blood, and none was a drug addict.

Adult↗
PubMed1981

The influence of pH on phosphate transport into rat renal brush border membrane vesicles.

Sodium-dependent transport of inorganic phosphate into brush border membrane vesicles is strongly influenced by altering pH of the incubation medium (pHo). At constant total phosphate concentration an increase in pHo leads to an increase in the uptake of inorganic phosphate. Uptake of inorganic phosphate, however, is not affected by the intravesicular pH (pHi) or by transmembrane pH differences (pHo--pHi). If initial phosphate uptake is studied as a function of total phosphate concentration in the medium the half saturation concentration increases when pHo is raised from 6.3--6.9 but remains unaltered between pHo 6.9 and 7.8 Vmax increases about 3-fold between pHo 6.3 and 6.9 and by a factor of about 1.6 between pHo 6.9 and 7.4. The pHo- dependence of phosphate uptake is diminished by increasing sodium concentrations. Altering transmembrane electrical potential difference by potassium + valinomycin-induced diffusion potentials or by anion replacement fails to demonstrate electrogenicity of sodium-phosphate cotransport. Experiments using a potential-sensitive fluorescent dye, however, indicate a vesicle inside positive electrical potential difference when inorganic phosphate is added. The phosphate-induced alterations in the electrical potential difference are sodium-dependent and more pronounced at low pHo values. Together with earlier observations these results suggest that translocation of inorganic phosphate across the proximal tubular brush border membrane is mediated by cotransport of 2 sodium ions with one either monovalent or divalent phosphate molecule according to its availability in the tubular fluid. The pH sensitivity of this transport system is rather due to alterations in the transport system itself than to pH- dependent alterations in the ratio of monovalent to divalent phosphate.

Animals↗
PubMed1981

Small nuclear RNA molecules that regulate nuclease accessibility in specific chromatin regions of meiotic cells.

One of the factors regulating the accessibility of specific DNA sequences to endonuclease nicking during meiosis is a group of small nuclear RNA molecules, 125 nucleotides in length and transcribed by RNA polymerase III. These molecules (referred to as PsnRNA) are synthesized during meiotic prophase, when chromosomes are undergoing homologous pairing or are already paired. Accessibility to the meiotically active DNA sequences (P DNA) depends on an as-yet-undefined alteration in chromatin structure. PsnRNA is a critical factor in the alteration; it cannot be replaced by other forms of RNA. The specificity of the chromatin sites altered by PsnRNA appears to be a function of sequence complementarity between it and P DNA. Under in vivo conditions the effective action of PsnRNA depends on homologous chromosome pairing. Chromatin sites housing P-DNA sequences in nuclei isolated from cells lacking homologous pairing are not affected by meiotic endonuclease or DNAse II. Accessibility to these sites can be effected by incubation of the nuclei with PsnRNA, but only if the nuclei are from zygotene-pachytene cells. Analyses of pachytene nuclei preincubated with PsnRNA indicate that PsnRNA renders chromatin accessible to at least two endonucleases, meiotic endonuclease and DNAase II, and that it also limits such accessibility to regions housing the complementary P-DNA sequences.

Base Sequence↗
PubMed1981

A serological study of cytomegalovirus and herpes simplex virus infections in Peninsular Malaysia.

Healthy Malaysians from various parts of Peninsular Malaysia were examined for CF antibodies against cytomegalovirus (CMV) and herpes simplex virus (HSV) type 2. CMV antibodies were detected in 1114 out of 1556 persons (71.6%) and HSV antibodies were detected in 954 persons out of 1554 (61.4%). The age distribution patterns were similar for the two infections, with maximum prevalence at 5 - 14 years of age. Prevalence was higher in women than in men. There were no significant differences among the Malay, Chinese, and Indian groups of the population with respect to CMV, 72 - 78% possessing antibodies, but in the case of HSV, 76% of the Chinese had antibodies, compared with 57 - 60% of the Malays and Indians. More than 90% of newborn infants had CMV and HSV CF antibodies, confirming the highly immune status of childbearing women in Malaysia. No CMV-specific IgM was detected in the Malaysian neonates examined but this does not exclude the possibility of congenital infection.

Adolescent↗
PubMed1980

Cytomegalovirus complement-fixing IgM antibody.

Cytomegalovirus (CMV)-specific IgM that fixes complement in the presence of CMV antigen was demonstrated in sera from five patients with primary CMV infection. The CF reaction, demonstrable in the IgM fractions of the sera, was not affected significantly by absorption with aggregated IgG but was abolished by treatment with 2-mercaptoethanol. The IgM antibody was readily detected in CF tests with crude cell-extract antigens, prepared from CMV-infected tissue culture cells, or with purified enveloped-virion antigen but not with CMV-soluble antigens.

Antibodies, Viral↗