| protoconch | <zoology> The embryonic shell, or first chamber, of ammonites and other cephalopods. Origin: Proto- + conch. Source: Websters Dictionary (01 Mar 1998) |
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| protocone | The mesiolingual cusp of an upper molar tooth in a mammal. Origin: proto-+ G. Konos, cone (05 Mar 2000) |
| protoconid | The mesiolingual cusp of a lower molar tooth in a mammal. (05 Mar 2000) |
| protocoproporphyria | Enhanced faecal excretion of proto-and coproporphyrins. (05 Mar 2000) |
| protocoproporphyria hereditaria | Porphyria characterised by abdominal pain and neuropsychiatric abnormalities, by dermal sensitivity to light and mechanical trauma, by increased faecal excretion of proto-and coproporphyrin, and by increased urinary excretion of d-aminolevulinic acid, porphobilinogen, and porphyrins; due to a deficiency of protoporphyrinogen oxidase; autosomal dominant inheritance. Synonym: protocoproporphyria hereditaria, South African type porphyria. (05 Mar 2000) |
| Protoctista | A kingdom of eukaryotes incorporating the algae and the protozoans that comprise the presumed ancestral stocks of the fungi, plant, and animal kingdoms; they lack the developmental pattern stemming from a blastula, typical of animals, the pattern of embryo development typical of plants, and development from spores as in the fungi. Included in Protoctista are the nucleated algae and seaweeds, the flagellated water molds, slime molds and slime nets, and the protozoa; unicellular, colonial, and multicellular organisms are included, but the complex development of tissues and organs of plants and animals is absent. The term Protoctista replaces the term Protista, which connotes single-celled or acellular organisms, whereas the basal pre-plant (Protophyta) and pre-animal (Protozoa) assemblages incorporated in Protoctista include many multicellular forms, since multicellularity appears to have evolved independently a number of times within these primitive groups. Origin: G. Protos, the first, + ktizo, to establish (05 Mar 2000) |
| protoderm | The undifferentiated cells of very young embryos, from which the primary germ layers will evolve. Origin: proto-+ G. Derma, skin (05 Mar 2000) |
| protodiastolic | Early diastolic, relating to the beginning of cardiac diastole. (05 Mar 2000) |
| protoduodenum | The first part of the duodenum which extends from the gastroduodenal pylorus as far as the major duodenal papilla and develops from the caudal foregut of the embryo; it has no plicae circulares and is the seat of the duodenal glands. (05 Mar 2000) |
| protoerythrocyte | A primitive erythroblast. (05 Mar 2000) |
| protofilament | <cell biology> One way of viewing microtubule structure is to consider it to be built of (usually) 13 protofilaments arranged in parallel. (18 Nov 1997) |
| protogen | <biochemistry> 1,2 dithiolane 3 valeric acid. Regarded as a coenzyme in the oxoglutarate dehydrogenase complex of the citric acid cycle. Involved generally in oxidative decarboxylations of _ keto acids. A growth factor for some organisms. (18 Nov 1997) |
| protogine | <chemical> A kind of granite or gneiss containing a silvery talcose mineral. Origin: Proto- + root of Gr. To be born: cf. F. Protogynae. Source: Websters Dictionary (01 Mar 1998) |
| protogonoplasm | A differentiated mass of cytoplasm in a protozoan, which forms the substance of later developing reproductive bodies. Origin: proto-+ G. Gonos, seed, + plasma, a thing formed (05 Mar 2000) |
| protogynous | Having the female sex organs maturing before the male, of a flower, shedding the pollen after the stigma has ceased to be receptive. Compare: protandrous. (09 Oct 1997) |