Absorption of amino penicillins from everted rat intestine.

1. Using an in vitro everted gut sac method based on that of Wilson & Wiseman (1954), a number of amino penicillins were tested in order to identify the involvement of any specialized transport mechanisms in their absorption across rat intestine. 2. Only one of the amino penicillins, cyclacillin (1-amino-cyclohexyl penicillin) was shown to be actively transported. The other penicillins appeared to diffuse passively across the intestine. 3. Cyclacillin was found to concentrate against a gradient at 37 degrees C but not at 19 degrees C. 4. Transport of cyclacillin across the mucosal membrane was saturated at mucosal concentrations greater than 1000 microgram/ml. 5. The rate of the forward flux of cyclacillin was many times that of its back flux. 6. No relationship between the active transport of cyclacillin and that of amino acids could be demonstrated.     

Growth, morbidity, and mortality in a cohort of institutionalized HIV-1-infected African children

OBJECTIVE: As a result of the HIV epidemic in Africa, much debate exists on whether institutionalized compared with community-based care provides optimum management of infected children. Previous reports calculated 89% mortality by age 3 years among outpatients in Malawi. No similar data are available for infected children in institutionalized care. We characterized patterns of morbidity and mortality among HIV-1-infected children residing at an orphanage in Nairobi. METHODS: Medical records for 174 children followed over 5 years were reviewed. Mortality was analyzed by Kaplan-Meier methods with adjustment to account for survival in the community before admission. Anthropometric indices were calculated to include mean z scores for weight for length and length for age. Low indices reflected wasting and stunting. Opportunistic infections were documented. RESULTS: Of 174 children, 64 had died. Survival was 70% at age 3 years. Morbidity included recurrent respiratory tract infections, gastroenteritis, parotitis, and lymphoid interstitial pneumonitis. No new cases of tuberculosis disease were noted after admission. Mean z scores for length for age suggested overall stunting (z = -1.65). Wasting was not observed (z = -0.39). CONCLUSION: The optimal form of care for HIV-infected children in resource-poor settings may be the development of similar homes. Absence of tuberculosis disease in long-standing residents may have contributed to improved survival. Stunting in the absence of wasting implied that growth was compromised by opportunistic infections and other cofactors.     

Genetic evidence on the origins of Indian caste populations

The origins and affinities of the approximately 1 billion people living on the subcontinent of India have long been contested. This is owing, in part, to the many different waves of immigrants that have influenced the genetic structure of India. In the most recent of these waves, Indo-European-speaking people from West Eurasia entered India from the Northwest and diffused throughout the subcontinent. They purportedly admixed with or displaced indigenous Dravidic-speaking populations. Subsequently they may have established the Hindu caste system and placed themselves primarily in castes of higher rank. To explore the impact of West Eurasians on contemporary Indian caste populations, we compared mtDNA (400 bp of hypervariable region 1 and 14 restriction site polymorphisms) and Y-chromosome (20 biallelic polymorphisms and 5 short tandem repeats) variation in approximately 265 males from eight castes of different rank to approximately 750 Africans, Asians, Europeans, and other Indians. For maternally inherited mtDNA, each caste is most similar to Asians. However, 20%-30% of Indian mtDNA haplotypes belong to West Eurasian haplogroups, and the frequency of these haplotypes is proportional to caste rank, the highest frequency of West Eurasian haplotypes being found in the upper castes. In contrast, for paternally inherited Y-chromosome variation each caste is more similar to Europeans than to Asians. Moreover, the affinity to Europeans is proportionate to caste rank, the upper castes being most similar to Europeans, particularly East Europeans. These findings are consistent with greater West Eurasian male admixture with castes of higher rank. Nevertheless, the mitochondrial genome and the Y chromosome each represents only a single haploid locus and is more susceptible to large stochastic variation, bottlenecks, and selective sweeps. Thus, to increase the power of our analysis, we assayed 40 independent, biparentally inherited autosomal loci (1 LINE-1 and 39 Alu elements) in all of the caste and continental populations (approximately 600 individuals). Analysis of these data demonstrated that the upper castes have a higher affinity to Europeans than to Asians, and the upper castes are significantly more similar to Europeans than are the lower castes. Collectively, all five datasets show a trend toward upper castes being more similar to Europeans, whereas lower castes are more similar to Asians. We conclude that Indian castes are most likely to be of proto-Asian origin with West Eurasian admixture resulting in rank-related and sex-specific differences in the genetic affinities of castes to Asians and Europeans.     

Morphological analysis of degeneration and regeneration of syncytiotrophoblast in first trimester placental villi during organ culture

We have recently shown using dansyl-L-lysine exclusion studies that the release of human chorionic gonadotrophin (HCG) in conjunction with L- lactate dehydrogenase (LDH) from first trimester villi during organ culture is symptomatic of syncytiotrophoblast degeneration. The purpose of this study was to examine chorionic villi at the ultrastructural level in order to determine events occurring during organ culture. The tissue was sampled after 0, 24, 48 and 120 h in culture and processed for electron microscopy. In addition to confirming the previously recorded syncytial degeneration, the electron micrographs showed clearly the generation of a new syncytiotrophoblast layer. The new layer, derived from differentiating cytotrophoblast cells, was largely formed by 48 h and was maintained for at least 120 h in culture. This study demonstrates a model which provides an opportunity to study the differentiation of cytotrophoblast cells whilst they retain their anatomical relationships within the villous structure.      

Activation of normal murine B cells by Echinococcus granulosus.

Echinococcus granulosus protoscolex (PSC) infection of BALB/c mice led, after 4 days, to raised numbers of cells forming plaques with trinitrophenyl-treated sheep red cells and bromelain-treated mouse red cells. The findings were similar in athymic and euthymic CBA mice. Activation of B cells was accompanied by secretion of immunoglobulin, as indicated by the reverse plaque technique. In addition, co-culture of PSC with the 7OZ/3 pre-B-cell led to the induction of differentiation, resulting in the expression of surface immunoglobulin (Ig). It is concluded that E. granulosus is a polyclonal activator of B cells inducing both transformation and differentiation, and that the effect is thymus-independent.     

Mutation of the signal peptide region of the bicistronic gene DSPP affects translocation to the endoplasmic reticulum and results in defective dentine biomineralization

Dentine dysplasia type II is an autosomal dominant disorder in which mineralization of the dentine of the primary teeth is abnormal. On the basis of the phenotypic overlap between, and shared chromosomal location with, dentinogenesis imperfecta type II, a second disorder of dentine mineralization, it has been proposed that the two conditions are allelic. As recent studies have shown that dentinogenesis imperfecta type II results from mutation of the bicistronic dentine sialophosphoprotein gene (DSPP ), we have tested this hypothesis by sequencing DSPP in a family with a history of dentine dysplasia type II. Our results have shown that a missense change, which causes the substitution of a tyrosine for an aspartic acid in the hydrophobic signal peptide domain of the protein, underlies the phenotype in this family. Biochemical analysis has further demonstrated that this mutation causes a failure of translocation of the encoded proteins into the endoplasmic reticulum, and is therefore likely to lead to a loss of function of both dentine sialoprotein and dentine phosphoprotein.     

Mutation of the gene encoding fibrillin-2 results in syndactyly in mice

Fibrillins are large, cysteine-rich glycoproteins that form microfibrils and play a central role in elastic fibrillogenesis. Fibrillin-1 and fibrillin-2, encoded by FBN1 on chromosome 15q21.1 and FBN2 on chromosome 5q23-q31, are highly similar proteins. The finding of mutations in FBN1 and FBN2 in the autosomal dominant microfibrillopathies Marfan syndrome (MFS) and congenital contractural arachnodactyly (CCA), respectively, has highlighted their essential role in the development and homeostasis of elastic fibres. MFS is characterized by cardiovascular, skeletal and ocular abnormalities, and CCA by long, thin, flexed digits, crumpled ears and mild joint contractures. Although mutations arise throughout FBN1, those clustering within exons 24-32 are associated with the most severe form of MFS, so-called neonatal MFS. All the mutations described in CCA occur in the "neonatal region" of FBN2. Both MFS and CCA are thought to arise via a dominant negative mechanism. The analysis of mouse mutations has demonstrated that fibrillin-1 microfibrils are mainly engaged in tissue homeostasis rather than elastic matrix assembly. In the current investigation, we have analysed the classical mouse mutant shaker-with-syndactylism using a positional candidate approach and demonstrated that loss-of-function mutations outside the "neonatal region" of Fbn2 cause syndactyly in mice. These results suggest that phenotypes distinct from CCA may result in man as a consequence of mutations outside the "neonatal region" of FBN2.