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Biomedical subjects

M Klein

Publications and source records attributed to M Klein.

At least 379 records · Page 21Linked to original sources
PubMed1993

Synthesis and immunological characterization of a 134-mer synthetic peptide corresponding to the N-terminal half of the HIV-1 nucleoprotein, p24.

A 134-mer peptide corresponding to the N-terminal sequence of p24 (residues 146-279 of the gag gene product of the LAV strain) was chemically synthesized using highly optimised protocols on an ABI 430A synthesizer. The crude peptide was obtained by treating the peptide-resin with HF, then purified by a combination of size exclusion and RP-HPLC. One hundred milligram of 90% pure 134-mer can be obtained within a month. Both mice and rabbit polyclonal antisera raised against a commercial preparation of recombinant p24, and a pooled sera from HIV-1 infected individuals reacted strongly with the 134-mer peptide in ELISA. Both mice and rabbits immunized with the free peptide emulsified in Freund's complete adjuvant generated strong anti-peptide and anti-p24 antibody responses as judged by immunoblots and ELISAs. Immunodominant epitopes were mapped to residues 201-227 (LKETINEEAAEWDRVHPVHAGPIAPG). These B-cell epitopes had previously been identified by mouse monoclonal antibodies raised against HIV-1 virus or gag gene products. Furthermore, murine T-cell lines generated against the 134-mer peptide were found to respond to two short peptides, P24B (residues 195-215) and P24D1 (residues 268-279). These two T-cell epitopes were previously reported as human helper T-cell and CTL epitopes, respectively. These results clearly indicate that the synthetic 134-mer peptide could elicit both T- and B-cell responses to HIV-1 similar to those obtained with the natural viral gag protein, and could be useful for the development of a synthetic HIV vaccine.

Amino Acid Sequence↗
PubMed1993

Characterization of pertussis toxin analogs containing mutations in B-oligomer subunits.

The S2, S3, and S4 subunit genes of pertussis toxin (PT) from Bordetella pertussis were subjected to site-directed mutagenesis, and the resultant PT analogs were assayed for altered biological properties. PT analogs S2(T91,R92,N93) delta and S2(Y102A,Y103A) exhibited reduced binding to fetuin. Several PT analogs with mutations in the S2, S3, or S4 subunit showed reduced in vitro toxicity, as measured in the Chinese hamster ovary (CHO) cell clustering assay. In particular, PT analogs S3(Y82A) and S3(I91,Y92,K93) delta retained 10% or less residual toxicity. These mutants also exhibited significantly lower mitogenic and hemagglutinating activities and reduced in vivo activities, as measured by the histamine sensitization and leukocytosis assays. The S4(K54A,K57A) PT analog had significantly reduced CHO cell clustering activity, though other biological activities remained unaffected. PT analogs S1(E129G)/S3(Y82A) and S1(E129G)/S3(I91,Y92,K93) delta displayed a cumulative effect of the S1 and S3 mutations for both in vitro and in vivo toxic activities. These PT analogs, as well as S1(R9K,E129G)/S3(K82A) and S1(R9K,E129G)/S3(I91,Y92,K93) delta, still expressed an epitope which elicits a neutralizing antitoxin antibody and were protective in the mouse intracerebral challenge test. Recombinant pertussis vaccines based on PT analogs with detoxifying mutations in multiple subunits may thus represent the next generation of improved whooping cough vaccines.

Amino Acid Sequence↗
PubMed1993

Immunogenicity of overlapping synthetic peptides covering the entire sequence of Haemophilus influenzae type b outer membrane protein P2.

Haemophilus influenzae type b is a major cause of bacterial meningitis in young children. Antibodies against the outer membrane protein P2 are protective in the infant rat model of bacteremia. To identify conserved, surface-exposed, and protective epitopes of P2, 17 overlapping peptides covering the entire sequence of the protein were synthesized. Antisera from mice, guinea pigs, and rabbits raised against chromatographically purified P2 were tested for their reactivities to the peptides by enzyme-linked immunosorbent assays (ELISA). Three major linear immunodominant B-cell epitopes were mapped to residues 53 to 81, 241 to 265, and 314 to 341 of mature P2. Human convalescent-phase antisera also reacted strongly with these three epitopes. Rabbit antisera against all peptide-keyhole limpet hemocyanin conjugates except two peptides containing residues 8 to 19 and 302 to 319 recognized the corresponding peptides in ELISA and reacted with P2 on immunoblots. Immunization with all unconjugated peptides, except the 19 N-terminal residues, induced very strong peptide-specific antibody responses, and these antisera reacted with P2 on immunoblots. Rabbit antisera raised against peptides corresponding to residues 1 to 14, 125 to 150, 193 to 219, and 241 to 319 also recognized P2 purified from H. influenzae nontypeable isolates. Identification of these immunodominant B-cell epitopes and conserved regions is a first step toward the rational design of a universal H. influenzae vaccine.

Amino Acid Sequence↗
PubMed1993

Identification of tRNAs incorporated into wild-type and mutant human immunodeficiency virus type 1.

We have identified the tRNAs which are incorporated into both wild-type human immunodeficiency virus type 1 strain IIIB (HIV-1IIIB) produced in COS-7 cells transfected with HIV-1 proviral DNA and mutant, noninfectious HIV-1Lai particles produced in a genetically engineered Vero cell line. The mutant proviral DNA contains nucleotides 678 to 8944; i.e., both long terminal repeats and the primer binding site are absent. As analyzed by two-dimensional polyacrylamide gel electrophoresis, both mutant and wild-type HIV-1 contain four major-abundance tRNA species, which include tRNA(1,2Lys), tRNA(3Lys) (the putative primer for HIV-1 reverse transcriptase) and tRNA(Ile). Identification was accomplished by comparing the electrophoretic mobilities and RNase T1 digests with those of tRNA(3Lys) and tRNA(1,2Lys) purified from human placenta and comparing the partial nucleotide sequence at the 3' end of each viral tRNA species with published tRNA sequences. Thus, the absence of the primer binding site in the mutant virus does not affect tRNA(Lys) incorporation into HIV-1. However, only the wild-type virus contains tRNA(3Lys) tightly associated with the viral RNA genome. The identification of the tightly associated tRNA as tRNA(3Lys) is based upon an electrophoretic mobility identical to that of tRNA(3Lys) and the ability of this RNA to hybridize with a tRNA(3Lys)-specific DNA probe. In addition to the four wild-type tRNA species, the mutant HIV-1-like particle contains two tRNA(His) species and three tRNA-sized species that we have been unable to identify. Their absence in wild-type virus makes it unlikely that they are required for viral infectivity.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Joint hypermobility and fibromyalgia in schoolchildren.

OBJECTIVES: To test the hypothesis that joint hypermobility may play a part in the pathogenesis of pain in fibromyalgia, schoolchildren were examined for the coexistence of joint hypermobility and fibromyalgia. METHODS: The study group consisted of 338 children (179 boys, 159 girls; mean age 11.5 years, range 9-15 years) from one public school in Beer-Sheva, Israel. In the assessment of joint hypermobility, the criteria devised by Carter and Bird were used. Any child who met at least three of five criteria was considered to have joint hypermobility. Children were considered to have fibromyalgia if they fulfilled the 1990 American College of Rheumatology criteria for the diagnosis of fibromyalgia, namely, widespread pain in combination with tenderness of 11 or more of the 18 specific tender point sites. The blind assessments of joint hypermobility (by AG) and fibromyalgia (by DB) were carried out independently. RESULTS: Of the 338 children 43 (13%) were found to have joint hypermobility and 21 (6%) fibromyalgia; 17 (81%) of the 21 with fibromyalgia had joint hypermobility and 17 (40%) of the 43 with joint hypermobility had fibromyalgia. Using chi 2 statistical analysis, joint hypermobility and fibromyalgia were found to be highly associated. CONCLUSIONS: This study suggests that there is a strong association between joint hypermobility and fibromyalgia in schoolchildren. It is possible that joint hypermobility may play a part in the pathogenesis of pain in fibromyalgia. More studies are needed to establish the clinical significance of this observation.

Adolescent↗
PubMed1993

Vitreous levels of the insulin-like growth factors I and II, and the insulin-like growth factor binding proteins 2 and 3, increase in neovascular eye disease. Studies in nondiabetic and diabetic subjects.

Retinal capillary nonperfusion results in neovascularization of the eye, which is restricted to the retina in less severe cases and progresses to the anterior chamber and the iris angle in the most advanced case, called rubeosis. This angioneogenesis may be induced by the release of retinal growth factors into the vitreous. This study compared levels of the IGF-I and IGF-II, and of the IGF binding protein-2 (IGFBP-2) and IGFBP-3 in vitreous from three groups with different degrees of retinal ischemia, as judged by the extent of neovascularization: a control group without new vessel formation, retinal neovascularization in patients with proliferative diabetic retinopathy, and massive ischemia of various causes resulting in rubeosis. IGF-I and IGFBP-3 were increased 10- and 13-fold in rubeosis (P << 0.01) compared with no ischemia (n = 10), while IGF-II and IGFBP-2 were elevated 2.7- and 4.3-fold (P < 0.01). Within the rubeosis group similar changes were observed independently of the cause of ischemia, which was central vein occlusion, ischemic ophthalmopathy, or intraocular tumor in seven cases and diabetic retinopathy in three samples from two patients. Vitreous from patients with proliferative diabetic retinopathy but without rubeosis (n = 16) contained 2.5- and 2.2-fold elevated levels of IGF-I and of IGFBP-2 (P < 0.05), while IGF-II and IGFBP-3 were increased 1.4- and 1.6-fold, which was not significant. We conclude that: (a) ischemia appears to be a strong stimulus for the local production of IGF-I and -II and of IGFBP-2 and -3 in the eye. (b) Changes in IGF-I and IGFBP-2 in proliferative diabetic retinopathy may be secondary to local ischemia rather than being specific for diabetic retinopathy. (c) IGF-I and IGFBP-3 may play a role in mediating angioneogenesis in the eye.

Carrier Proteins↗
PubMed1993

Clinical trials with a polycrystalline alumina dental implant.

The Tübingen polycrystalline alumina implant utilizes bony apposition as the method of stabilization. Its cylindrical configuration allows the implant site to be prepared by use of ultra-low-speed drills. This study focused on the use of the implant as a single-tooth, free-standing device. Thirty patients were selected. Devices were followed for five years. The implants were placed in one of two applications: immediate extraction site or healed edentulous ridge. A simple purse-string suture technique was used for closure. Periodic observations were recorded. Of the 30 planned implants, all have been completed to date. Twenty-five of the 30 have been considered successful. Twenty-three of the 25 successes were from the immediate extraction group. Only 2 of 5 were successful in the healed ridge group. Due to the structural requirements of the Tübingen implant, its size makes it usable only in wider-than-average edentulous ridges. The success rate was 83.3%, and for those devices placed in immediate extraction sites, a success rate of 92% was recorded.

Adolescent↗
PubMed1993

[Abnormalities of the muscular bioenergetics in Steinert's disease].

The thenar muscles and gastrocnemius of a patient with myotonic dystrophy were investigated, at rest, by phosphorus nuclear magnetic resonance spectroscopy. A decrease in phosphocreatine level and an increase in inorganic phosphate and phosphodiester levels were found in the gastrocnemius, which was clinically spared, whilst the thenar muscles, which were wasted and affected by myotonia, exhibited only an increased inorganic phosphate level and an elevated pH. These findings were comparable with those found in other muscular disorders, such as Duchenne's and Becker's dystrophies, as well as in limb girdle dystrophy. They suggested that the abnormalities observed were unrelated to myotonia or wasting, and the possibility of a secondary mitochondrial disorder in myotonic dystrophy, is to be considered.

Adult↗
PubMed1993

A computerized tomography (CT) scan appliance for optimal presurgical and preprosthetic planning of the implant patient.

This article describes the technique for using the CT (computerized axial tomography) scans, with specially designed software and an adjunct appliance, for accurate planning of dental implants and implant-supported restorations. The available bone can be evaluated, surgical problems anticipated, and errors in placement avoided. The learning objective of this article is an enhanced knowledge of the extended application of the CT scans and the use of the orientation and immobilization appliance.

Dental Implantation, Endosseous↗
PubMed1993

[Disorders of hemostasis in dysthyroidism].

Many potentially severe hemostatic disorders have been reported in thyroid diseases. Hyperthyroidism has been associated with thrombocytopenia, coagulation factor abnormalities, and decreased fibrinolytic and plasminogen activities. In hypothyroidism, potentially severe hemorrhagic disorders have been reported, including platelet function abnormalities and coagulation factor alterations such as acquired von Willebrand disease.

Blood Coagulation Disorders↗
PubMed1993

The effectiveness of family practice maternity care. A cross-cultural and environmental view.

All 17 studies of family practice maternity care have shown reduced procedure rates for comparable populations of women cared for by family physicians versus those cared for by obstetricians, while maternal and infant outcomes are as good or better for the patients of family practitioners. System issues are the most predictive of positive outcomes such that in settings in which continuity and intimacy is high and women of no defined risk are cared for by providers specifically oriented to such care, outcomes are the best. In contrast, when such women are cared for by providers specifically oriented for high-risk or tertiary settings, their care becomes medicalized and they become sick. Staff attitudes, rules, and organizational structures are more predictive of outcome than professional labels. Family physicians in all settings can do more to lower their intervention rates and "humanize" care.

Canada↗
PubMed1993

Differential cyclic AMP dependence of facilitation at Aplysia sensorimotor synapses as a function of prior stimulation: augmentation versus restoration of transmitter release.

Synaptic facilitation at sensory-to-motor neuron synapses in Aplysia is a mechanism contributing to a simple form of learning called behavioral sensitization. Previous work has shown that facilitation is mediated in part by the neurotransmitter 5-HT acting through cAMP to broaden presynaptic action potentials and thus increase transmitter release from the sensory neuron terminals. Other studies have indicated that 5-HT causes facilitation by more than one mechanism, depending on whether the synapse has first been depressed by prior stimulation. The present study examines the involvement of cAMP in facilitation at depressed synapses by utilizing the adenylyl cyclase activator 7 beta-desacetyl-7 beta-[gamma-(N-methylpiperazino)-butyryl] forskolin (7B-forskolin) and 5-HT separately and in combination. Facilitation at relatively rested synapses can be mimicked with application of 7B-forskolin, whereas transmission at synapses that have been subjected to repeated stimulation is not affected. The forskolin derivative by itself increases cAMP levels in sensory neurons and potentiates 5-HT-induced stimulation of cAMP 2-10-fold. Nonetheless, joint application of 7B-forskolin and 5-HT at submaximal concentrations to depressed synapses causes the same amount of facilitation as 5-HT alone. This finding implies that facilitation by 5-HT at repeatedly stimulated synapses is not mediated by cAMP alone. In addition, facilitation by 7B-forskolin at relatively rested synapses can occur without prolongation of action potentials, suggesting that cAMP can act in more than one way to enhance transmission. Taken together with earlier findings, the present results suggest that at least three distinct processes participate in facilitation by 5-HT.

Action Potentials↗