Female marmoset monkeys (Callithrix jacchus) can be identified from the chemical composition of their scent marks.

The present study analyzed 42 organic solvent extracts of scent mark pools from five dominant female common marmosets by gas chromatography (GC) and combined GC and mass spectrometry. We determined whether there were qualitative or quantitative differences between the chemical composition of scent marks from individual females. Gas chromatography and mass spectral analysis detected the same 162 chemicals in 86% (36/42) of scent mark pools from five dominant females. This near identical chemical composition of scent marks suggested there were few, if any, qualitative differences between the chemical composition of scent marks from individual females. Instead, quantitative differences in scent may provide the key factor distinguishing individual females. Using the relative concentration of highly volatile chemicals detected by GC in scent marks, linear discriminant analysis classified scent mark pools to their correct donor approximately 91% of the time. Such highly reliable statistical matching of scent to donor suggested that each individual female common marmoset has a unique ratio of highly volatile chemicals in their scent marks which may permit individual identification of females from odors in their scent alone.     

Computerized tomographic imaging of cryosurgical iceball formation in brain

Computerized tomography (CT) was used to monitor the exact anatomical location and dimensions of the cryosurgical iceball within the brain. The gross and microscopic appearance of the tissue iceball was examined in both acute and chronic animals. Iceball formation was monitored in the brain of four dogs under a general anesthesia. The radiographic image of the iceball was that of a well-demarcated radiolucent sphere that disappeared upon thawing. The post-thaw contrast-enhanced CT scan revealed a zone of blood-brain barrier breakdown extending no more than 1 mm beyond the maximum diameter that the iceball had attained. Histological examination demonstrated a sharp transition from frankly necrotic brain within the iceball to the normal cytoarchitecture of the surrounding neuropil. The safety and efficacy of a neurosurgical ablative procedure depends on the precision with which it can be generated. The use of CT imaging to monitor the formation of the cryosurgical iceball offers the neurosurgeon a means to precisely control the size of the ablative lesion. Small deeply situated brain tumors can be incorporated into the iceball under direct CT observation, thereby ensuring the completeness of the cryoablation while minimizing damage to the surrounding brain.     

Generation of small mutation in large genomic fragments by homologous recombination: description of the technique and examples of its use

We have developed a technique of homologous recombination in bacteria which allows the mutagenesis of large genomic fragments cloned in cosmids. The desired mutation is first introduced into a plasmid clone and is then transferred to the appropriate cosmid clone by the means of double antibiotic selection coupled with phenotypic selection. We describe three different types of construct made by this technique.     

Topography and functions of sulfhydryl groups of the human erythrocyte glucose transport mechanism

Summary Membrane-impermeant and -permeant maleimides were applied to characterize the location and function of the sulfhydryl (SH) groups essential for the facilitated diffusion mediated by the human erythrocyte glucose transport protein. Three such classes have been identified. Type I SH is accessible to membrane-impermeant reagents at the outer (exofacial) surface of the intact erythrocyte. Alkylation of this class inhibits glucose transport; D-glucose and cytochalasin B protect against the alkylation. Type II SH is located at the inner (endofacial) surface of the membrane and is accessible to the membrane-impermeant reagent glutathione maleimide only after lysis of the erythrocyte. D-glucose enhances, while cytochalasin B reduces, the alkylation of Type II SH by maleimides. Reaction of Types I and II SH with an impermeant maleimide increases the half-saturation concentration for binding of D-glucose to erythrocyte membranes. By contrast, inactivation of Type III SH markedly decreases the half-saturation concentration for the binding of D-glucose and other transported sugars. Type III SH is inactivated by the relatively lipid-soluble reagents N-ethylmaleimide (NEM) and dipyridyl disulfide, but not by the impermeant glutathione maleimide. Type III SH is thus located in a hydrophobic membrane domain. A kinetic model constructed to explain these observations indicates that Type III SH is required for the translocation event in a hydrophobic membrane domain which leads to the dissociation of glucose bound to transport sites at the membrane surfaces.