Pregnancy Obstructs Involution Stage II of the Mammary Gland in Cows: General Biological Implications

*Background*
Repeated research findings over the last 4 decades show that involution of mammary glands in dairy cows did not regress to same extend as that noticed in other mammalian species.

*Methodology/Principal Findings*
We took an advantage of a rare event in the normal modern dairy farming: A cow that was false-positively identified as being pregnant was "dried up" (i.e., induced into involution) conventionally about 60 before her expected parturition. This cow was culled, and samples of her mammary gland tissue were examined for gross histology. In this study we demonstrate for the first time that modern dairy cow may undergo extensive obliteration of the lobular-alveolar structure, as expected in involution stage II. 

*Conclusions/Significance*
We conclude that lack of histological evidence for the appearance of involution stage II in the vast majority of modern cow's population is related to the peculiar modern dairy husbandry, in which dairy cows are induced into involution still pregnant. Because retardation of involution stage II in pregnant mammals is most likely a general physiological phenomena, it might occurs in other mammals, particularly in lactating humans. Thus, based on basic comparative physiology considerations, we suggest that concurrent lactation and pregnancy should be considered as an independent risk factor for breast cancer

A Study of the Mechanism of Fouling of Ultrafiltration Membranes

159 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1979.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Membrane Processing of Citrus Extracts: Effects on Pectinesterase Activity and Cloud Stability

The U.S. team studied the role of cations and pH on thermolabile (TL-PE) and thermostable (TS-PE), permeation in ultrafiltration (UF) membranes, affinity to ion exchange membranes, mechanism of cation and pH activation, and effect on PE stability. An optimum pH and cation concentration exists for activity and UF permeation, which is specific for each cation type. Incomplete release of PE from a pectin complex resulted in low PE binding to cationic and anionic membranes. Incubation of PE at low pH increases the surface hydrophobicity, especially TL-PE, but the secondary structure of TL-PE is not greatly affected. The Israeli team showed that stable cloud colloidal constituents flocculate following the conversion of soluble to insoluble biopolymers. First, formation of pectic acid by pectinesterase activity is followed by the formation of calcium pectate gel. This process initiates a myriad of poorly defined reactions that result in juice clarification. Second, protein coagulation by heat resulted in flocculation of proteinacous bound cloud constituents, particularly after enzymatic pectin degradation. Pectinesterase activity is proposed to be an indirect cause for clarification; whereas binding of cloud constituents is the primary event in clarification by pectate gel and coagulated proteins. Understanding the mechanism of interaction of protein and pectic polymers is key to understanding cloud instability. Based on the above, it was hypothesized that the structure of pectin-protein coagulates plays a key role in cloud instability.</p